fix(unsquashfs): fix Fatal Error when using unsquashfs

When trying to push a big snap, snapcraft fails with the error

    FATAL ERROR: Data queue size is too large

This is a bug in unsquashfs tool 4.5. But it has been fixed in
4.6.1, the current stable.

This patch builds squashfs-tools version 4.6.1 from the GIT
repository, thus fixing this problem.

Fix #5132

snap/snapcraft.yaml

@@ -105,7 +105,6 @@ parts:
         - python3-distutils
         - python3-pkg-resources
         - python3.10-minimal
-        - squashfs-tools
         - xdelta3
     build-attributes:
       - enable-patchelf
@@ -139,6 +138,26 @@ parts:
       sed -i "${SNAPCRAFT_PART_INSTALL}/usr/lib/python3.10/site.py" \
         -e 's/^ENABLE_USER_SITE = None$/ENABLE_USER_SITE = False/'
 
+  squashfs-tools:
+    source: https://github.com/plougher/squashfs-tools
+    source-type: git
+    source-tag: "4.6.1"
+    after: ["snapcraft-libs"]
+    plugin: make
+    build-packages:
+      - help2man
+      - liblz4-dev
+      - liblzo2-dev
+    build-environment:
+      - CONFIG: "1"
+      - INSTALL_PREFIX: "${CRAFT_PART_INSTALL}/usr"
+      - LZMA_XZ_SUPPORT: "1"
+      - LZ4_SUPPORT: "1"
+      - LZO_SUPPORT: "1"
+      - XZ_SUPPORT: "1"
+    make-parameters:
+      - -C squashfs-tools
+
   libgit2:
     source: https://github.com/libgit2/libgit2/archive/refs/tags/v1.7.1.tar.gz
     source-checksum: sha256/17d2b292f21be3892b704dddff29327b3564f96099a1c53b00edc23160c71327