.so file being placed in /tmp/build_XXX directory

[danielricecodes]

Can someone help me out here? Why would a .so file be placed inside of a tmp directory?

Unable to load application: LoadError: /tmp/build_29fd2902/vendor/bundle/ruby/2.7.0/gems/extpp-0.0.9/ext/extpp/libruby-extpp.so:
cannot open shared object file: No such file or directory - 
/app/vendor/bundle/ruby/2.7.0/gems/red-arrow-4.0.0/lib/arrow.so

When I run heroku run bash, the file indeed doesn't exist there - it exists in /app/vendor instead.

My question is this: why is only that one .so file being placed there? Why would arrow.so be configured to link to a file that doesn't exist? What could cause something like this? I'm at a loss, so if anyone out there with a better understanding of how this buildpack works could point me in the right direction I'd really appreciate it.

Here's the full output from ldd on arrow.so showing the broken link to libruby-extpp.so in the wrong directory:

~ $ ldd /app/vendor/bundle/ruby/2.7.0/gems/red-arrow-4.0.0/lib/arrow.so 
	linux-vdso.so.1 (0x00007fffbcd6f000)
	libruby.so.2.7 => not found
	libarrow.so.500 => /app/.apt/usr/lib/x86_64-linux-gnu/libarrow.so.500 (0x00007f8fd7389000)
	libarrow-glib.so.500 => /app/.apt/usr/lib/x86_64-linux-gnu/libarrow-glib.so.500 (0x00007f8fd7243000)
	libgobject-2.0.so.0 => /app/.apt/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 (0x00007f8fd71e3000)
	/tmp/build_29fd2902/vendor/bundle/ruby/2.7.0/gems/extpp-0.0.9/ext/extpp/libruby-extpp.so => not found
	libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f8fd6fff000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f8fd6e0d000)
	libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f8fd6df2000)
	libbrotlienc.so.1 => /lib/x86_64-linux-gnu/libbrotlienc.so.1 (0x00007f8fd6d69000)
	libbrotlidec.so.1 => /lib/x86_64-linux-gnu/libbrotlidec.so.1 (0x00007f8fd6d5b000)
	libutf8proc.so.2 => /app/.apt/usr/lib/x86_64-linux-gnu/libutf8proc.so.2 (0x00007f8fd6d0c000)
	libre2.so.5 => /app/.apt/usr/lib/x86_64-linux-gnu/libre2.so.5 (0x00007f8fd6c9b000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f8fd6c95000)
	libcrypto.so.1.1 => /lib/x86_64-linux-gnu/libcrypto.so.1.1 (0x00007f8fd69bf000)
	libbz2.so.1.0 => /lib/x86_64-linux-gnu/libbz2.so.1.0 (0x00007f8fd69ac000)
	liblz4.so.1 => /lib/x86_64-linux-gnu/liblz4.so.1 (0x00007f8fd698b000)
	libsnappy.so.1 => /app/.apt/usr/lib/x86_64-linux-gnu/libsnappy.so.1 (0x00007f8fd697e000)
	libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f8fd6962000)
	libzstd.so.1 => /lib/x86_64-linux-gnu/libzstd.so.1 (0x00007f8fd68b9000)
	libcurl.so.4 => /lib/x86_64-linux-gnu/libcurl.so.4 (0x00007f8fd6828000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f8fd66d9000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f8fd66b6000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f8fd8a68000)
	libglib-2.0.so.0 => /app/.apt/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007f8fd658b000)
	libgio-2.0.so.0 => /app/.apt/usr/lib/x86_64-linux-gnu/libgio-2.0.so.0 (0x00007f8fd63aa000)
	libffi.so.7 => /lib/x86_64-linux-gnu/libffi.so.7 (0x00007f8fd639e000)
	libbrotlicommon.so.1 => /lib/x86_64-linux-gnu/libbrotlicommon.so.1 (0x00007f8fd637b000)
	libnghttp2.so.14 => /lib/x86_64-linux-gnu/libnghttp2.so.14 (0x00007f8fd6352000)
	libidn2.so.0 => /lib/x86_64-linux-gnu/libidn2.so.0 (0x00007f8fd632f000)
	librtmp.so.1 => /lib/x86_64-linux-gnu/librtmp.so.1 (0x00007f8fd630f000)
	libssh.so.4 => /lib/x86_64-linux-gnu/libssh.so.4 (0x00007f8fd62a1000)
	libpsl.so.5 => /lib/x86_64-linux-gnu/libpsl.so.5 (0x00007f8fd628e000)
	libssl.so.1.1 => /lib/x86_64-linux-gnu/libssl.so.1.1 (0x00007f8fd61fb000)
	libgssapi_krb5.so.2 => /lib/x86_64-linux-gnu/libgssapi_krb5.so.2 (0x00007f8fd61ae000)
	libldap_r-2.4.so.2 => /lib/x86_64-linux-gnu/libldap_r-2.4.so.2 (0x00007f8fd6156000)
	liblber-2.4.so.2 => /lib/x86_64-linux-gnu/liblber-2.4.so.2 (0x00007f8fd6145000)
	libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f8fd60d2000)
	libgmodule-2.0.so.0 => /app/.apt/usr/lib/x86_64-linux-gnu/libgmodule-2.0.so.0 (0x00007f8fd60cc000)
	libmount.so.1 => /lib/x86_64-linux-gnu/libmount.so.1 (0x00007f8fd606c000)
	libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f8fd603f000)
	libresolv.so.2 => /lib/x86_64-linux-gnu/libresolv.so.2 (0x00007f8fd6023000)
	libunistring.so.2 => /lib/x86_64-linux-gnu/libunistring.so.2 (0x00007f8fd5ea1000)
	libgnutls.so.30 => /lib/x86_64-linux-gnu/libgnutls.so.30 (0x00007f8fd5ccb000)
	libhogweed.so.5 => /lib/x86_64-linux-gnu/libhogweed.so.5 (0x00007f8fd5c94000)
	libnettle.so.7 => /lib/x86_64-linux-gnu/libnettle.so.7 (0x00007f8fd5c5a000)
	libgmp.so.10 => /lib/x86_64-linux-gnu/libgmp.so.10 (0x00007f8fd5bd4000)
	libkrb5.so.3 => /lib/x86_64-linux-gnu/libkrb5.so.3 (0x00007f8fd5af7000)
	libk5crypto.so.3 => /lib/x86_64-linux-gnu/libk5crypto.so.3 (0x00007f8fd5ac6000)
	libcom_err.so.2 => /lib/x86_64-linux-gnu/libcom_err.so.2 (0x00007f8fd5abf000)
	libkrb5support.so.0 => /lib/x86_64-linux-gnu/libkrb5support.so.0 (0x00007f8fd5ab0000)
	libsasl2.so.2 => /lib/x86_64-linux-gnu/libsasl2.so.2 (0x00007f8fd5a91000)
	libgssapi.so.3 => /lib/x86_64-linux-gnu/libgssapi.so.3 (0x00007f8fd5a4c000)
	libblkid.so.1 => /lib/x86_64-linux-gnu/libblkid.so.1 (0x00007f8fd59f5000)
	libpcre2-8.so.0 => /lib/x86_64-linux-gnu/libpcre2-8.so.0 (0x00007f8fd5965000)
	libp11-kit.so.0 => /lib/x86_64-linux-gnu/libp11-kit.so.0 (0x00007f8fd582f000)
	libtasn1.so.6 => /lib/x86_64-linux-gnu/libtasn1.so.6 (0x00007f8fd5817000)
	libkeyutils.so.1 => /lib/x86_64-linux-gnu/libkeyutils.so.1 (0x00007f8fd5810000)
	libheimntlm.so.0 => /lib/x86_64-linux-gnu/libheimntlm.so.0 (0x00007f8fd5804000)
	libkrb5.so.26 => /lib/x86_64-linux-gnu/libkrb5.so.26 (0x00007f8fd5771000)
	libasn1.so.8 => /lib/x86_64-linux-gnu/libasn1.so.8 (0x00007f8fd56ca000)
	libhcrypto.so.4 => /lib/x86_64-linux-gnu/libhcrypto.so.4 (0x00007f8fd5690000)
	libroken.so.18 => /lib/x86_64-linux-gnu/libroken.so.18 (0x00007f8fd5677000)
	libwind.so.0 => /lib/x86_64-linux-gnu/libwind.so.0 (0x00007f8fd564d000)
	libheimbase.so.1 => /lib/x86_64-linux-gnu/libheimbase.so.1 (0x00007f8fd563b000)
	libhx509.so.5 => /lib/x86_64-linux-gnu/libhx509.so.5 (0x00007f8fd55ed000)
	libsqlite3.so.0 => /lib/x86_64-linux-gnu/libsqlite3.so.0 (0x00007f8fd54c2000)
	libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007f8fd5487000)