Hello, i'm a XMake contributor and i'm trying to improve our GCC
modulemap support
i'm currently facing an issue with the path handling (i think so) of
headerunits, i don't know if i did anything wrong
i'm generating a modulemap file like
```
root F:/repos/xmake/tests/projects/c++/modules/user_headerunit
F:/repos/xmake/tests/projects/c++/modules/user_headerunit/src/header.hpp
build/.gens/user_headerunit/mingw/x86_64/release/rules/bmi/cache/headerunits/header.hpp.gcm
```
but when i supply this modulemap file to gcc to build the headerunit i'm
getting:
```
x86_64-w64-mingw32-g++ -c -m64 -std=c++20 -fmodules-ts
-D_GLIBCXX_USE_CXX11_ABI=0
-IF:\repos\xmake\tests\projects\c++\modules\user_headerunit\src
-fmodule-mapper=F:\msys64\tmp\.xmake\231130\modulemap.txt
-fmodule-header=user -fmodule-only -xc++-header -c -o
build\.gens\user_headerunit\mingw\x86_64\release\rules\bmi\cache\headerunits\header.hpp.gcm
header.hpp
F:\repos\xmake\tests\projects\c++\modules\user_headerunit\src/header.hpp:
error: unknown Compiled Module Interface: no such module
F:\repos\xmake\tests\projects\c++\modules\user_headerunit\src/header.hpp:5:
confused by earlier errors, bailing out
```
any idea on how to fix this ?
