New comment by meator on void-packages repository

https://github.com/void-linux/void-packages/pull/50183#issuecomment-2135947149

Comment:
> after several hours, i can't figure out how to fix cross compilation for `imhex`
> 
> please help

Worry not, I come to the rescue!

Here's a patch:

```patch
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,6 +29,12 @@
 set(CMAKE_MODULE_PATH "${IMHEX_BASE_FOLDER}/cmake/modules")
 include("${IMHEX_BASE_FOLDER}/cmake/build_helpers.cmake")
 
+# Void Linux flags for cross compiling libromfs
+set(NATIVE_CMAKE_C_COMPILER "$ENV{CC_host}")
+set(NATIVE_CMAKE_CXX_COMPILER "$ENV{CXX_host}")
+set(NATIVE_CMAKE_C_FLAGS "$ENV{CFLAGS_host}")
+set(NATIVE_CMAKE_CXX_FLAGS "$ENV{CXXFLAGS_host}")
+
 # Setup project
 loadVersion(IMHEX_VERSION)
 setVariableInParent(IMHEX_VERSION ${IMHEX_VERSION})
```

This is what's causing problems: https://github.com/WerWolv/libromfs/blob/master/generator/CMakeLists.txt#L5-L12 (`libromfs` isn't a part of `imhex`, it gets downloaded during the configure step[^1])

`ld` prints warnings about skipping aarch libraries when looking for libs. I believe that these warnings are harmless.

<details><summary>Here are the ld warnings.</summary>
<p>

```
...
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.so when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.a when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.so when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.a when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
[141/369] Linking CXX executable plugins/builtin/libromfs/generator/generator-builtin
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.so when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.a when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.so when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.a when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
[142/369] Linking CXX executable main/gui/main/gui/libromfs/generator/generator-imhex
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.so when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libstdc++.a when searching for -lstdc++
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.so when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libm.a when searching for -lm
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.so when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libc.a when searching for -lc
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
/usr/bin/ld: skipping incompatible /usr/aarch64-linux-gnu/usr/lib/libgcc_s.so.1 when searching for libgcc_s.so.1
...
```

</p>
</details>

These flags could be theoretically set through `$configure_args`, but the variable expansion gets pretty funky with `$CFLAGS_host` and `$CXXFLAGS_host`. `libromfs`'s build system disregards the relevant `NATIVE_CMAKE_` variables when set through the environment, so the only two solutions I see is passing `-DNATIVE_CMAKE_` to cmake (impossible to do [because of parameter expansion](https://github.com/void-linux/void-packages/blob/master/common/build-style/cmake.sh#L78)) or modifying the build system like my patch does.

[^1]: This is bad for obvious reasons, I believe that it pulls https://github.com/WerWolv/libromfs directly from master. This should probably be fixed.