Fix XZ build when bundled LZMA header shadows liblzma

[xiongxianfei]

Summary

This PR builds on #56 and fixes a long-standing XZ build failure where the bundled legacy LZMA SDK header shadows the system XZ Utils/liblzma header.

When both XZ_SUPPORT and legacy LZMA_SUPPORT are enabled, xz_wrapper.c includes <lzma.h> and expects the system liblzma header from liblzma-dev.

However, the Makefile adds bundled legacy LZMA include paths globally, including:

-I$(LZMA_ALT_DIR)

That can cause GCC to include:

./LZMA/lzmalt/lzma.h

instead of the system liblzma header:

/usr/include/lzma.h

The bundled legacy header does not define XZ/liblzma types such as lzma_vli, lzma_filter, and lzma_options_lzma, so the build fails.

Fix

This PR adds a small follow-up patch, patches/patch1.txt, and updates build.sh to apply all patch*.txt files in order.

The patch keeps legacy LZMA include paths for the legacy LZMA code, but removes them when compiling xz_wrapper.o, allowing <lzma.h> to resolve to the system liblzma header without hardcoding /usr/include/lzma.h.

Why not hardcode /usr/include/lzma.h?

Hardcoding this:

#include "/usr/include/lzma.h"

works on Ubuntu, but it is not portable to other Linux distributions, sysroots, cross-compilers, or custom install prefixes. Fixing the Makefile include path is more maintainable.

Tested

Tested with:

rm -rf squashfs4.3
./build.sh

cd squashfs4.3/squashfs-tools
make clean
make CC="gcc -H" > /tmp/sasquatch-build.log 2>&1
grep -i 'lzma.h' /tmp/sasquatch-build.log

Before:

./LZMA/lzmalt/lzma.h

After:

/usr/include/lzma.h

Also verified that the final binary links against liblzma:

ldd ./sasquatch | grep lzma

Related

• Builds on modern Ubuntu: Builds on modern Ubuntu #56
• Original lzma_vli / lzma_filter failure: I've done something wrong #6