meson: systemd-repart.standalone

Repart is growing into an important tool on its own, and users might
want to install newer versions on systems that have older systemd. Let's
make this easier by providing a standalone binary.

Related to systemd/mkosi#1228.

meson.build

@@ -1195,16 +1195,6 @@ endif
 
 #####################################################################
 
-libatomic = []
-if not cc.links('''#include <stdint.h>
- int main() {
- char i;
- __atomic_exchange_1(&i, 1, 0);
- return 1;
- }''',
- name : 'Atomic builtin requires -latomic')
- libatomic = cc.find_library('atomic')
-endif
 threads = dependency('threads')
 #if 0 /// UNNEEDED in elogind
 # librt = cc.find_library('rt')
@@ -1213,6 +1203,17 @@ libm = cc.find_library('m')
 libdl = cc.find_library('dl')
 libcrypt = cc.find_library('crypt')
 
+# On some architectures, libatomic is required. But on some installations,
+# it is found, but actual linking fails. So let's try to use it opportunistically.
+# If it is installed, but not needed, it will be dropped because of --as-needed.
+if cc.links('''int main(int argc, char **argv) { return 0; }''',
+ args : '-latomic',
+ name : 'libatomic')
+ libatomic = declare_dependency(link_args : '-latomic')
+else
+ libatomic = []
+endif
+
 crypt_header = conf.get('HAVE_CRYPT_H') == 1 ? '''#include <crypt.h>''' : '''#include <unistd.h>'''
 foreach ident : [
  ['crypt_ra', crypt_header],
@@ -1596,7 +1597,7 @@ conf.set10('HAVE_PAM', have)
 # want_qrencode = get_option('qrencode')
 # if want_qrencode != 'false' and not skip_deps
 # libqrencode = dependency('libqrencode',
-# version : '>= 4',
+# version : '>= 3',
 # required : want_qrencode == 'true')
 # have = libqrencode.found()
 # else
@@ -4133,6 +4134,24 @@ public_programs += executable(
 # install : true,
 # install_dir : rootbindir)
 # public_programs += exe
+#
+# if have_standalone_binaries
+# exe = executable(
+# elogind_repart_sources,
+# include_directories : includes,
+# c_args : '-DSTANDALONE',
+# link_with : [libshared_static,
+# libbasic,
+# libbasic_gcrypt,
+# libelogind_static],
+# dependencies : [threads,
+# libblkid,
+# libfdisk,
+# libopenssl],
+# install_rpath : rootpkglibdir,
+# install : true,
+# install_dir : rootbindir)
+# endif
 # endif
 #
 # executable(