Garbage in pkg-config on FreeBSD

Operating System Info

Other

Other OS

FreeBSD

OBS Studio Version

28.1.2

OBS Studio Version (Other)

No response

OBS Studio Log URL

N/A

OBS Studio Crash Log URL

No response

Expected Behavior

$ pkg-config libobs --cflags
-I/usr/local/include/obs -DHAVE_OBSCONFIG_H -mmmx -msse -msse2 -pthread

Current Behavior

$ pkg-config libobs --cflags
-I/usr/local/include/obs -DHAVE_OBSCONFIG_H -mmmx -msse -msse2 $\<$\<COMPILE_LANG_AND_ID:CUDA,NVIDIA\>:SHELL:-Xcompiler -pthread\> $\<$\<NOT:$\<COMPILE_LANG_AND_ID:CUDA,NVIDIA\>\>:-pthread\> 

Steps to Reproduce

0. pkg install obs-studio mercurial meson pkgconf
1. hg clone https://hg.sr.ht/~scoopta/wlrobs
2. cd wlrobs
3. hg checkout v1.0
4. meson setup _build
5. meson compile -C _build

cc: error: unknown argument '-pthread>'; did you mean '-pthreads'?
cc: error: no such file or directory: '$<$<COMPILE_LANG_AND_ID:CUDA,NVIDIA>:SHELL:-Xcompiler'
cc: error: no such file or directory: '$<$<NOT:$<COMPILE_LANG_AND_ID:CUDA,NVIDIA>>:-pthread>'

Anything else we should know?

Regressed by #6746 due to not sanitizing INTERFACE_COMPILE_OPTIONS. CC @PatTheMav, @yurivict

--- /usr/local/libdata/pkgconfig/libobs.pc	before
+++ /usr/local/libdata/pkgconfig/libobs.pc	after
@@ -1,10 +1,10 @@ Version: 28.1.2
 prefix=/usr/local
 exec_prefix=${prefix}
 libdir=/usr/local/lib
 includedir=/usr/local/include/obs
 
 Name: libobs
 Description: OBS Studio Library
 Version: 28.1.2
-Cflags: -I${includedir} -DHAVE_OBSCONFIG_H  
-Libs: -L${libdir} -lpthread
+Cflags: -I${includedir} -DHAVE_OBSCONFIG_H -mmmx -msse -msse2  $<$<COMPILE_LANG_AND_ID:CUDA,NVIDIA>:SHELL:-Xcompiler -pthread> $<$<NOT:$<COMPILE_LANG_AND_ID:CUDA,NVIDIA>>:-pthread>
+Libs: -L${libdir} -lobs -lpthread

Note, COMPILE_LANG_AND_ID:CUDA,NVIDIA comes from Threads::Threads

Reproduce the FreeBSD build with Meson and pkgconf, then inspect how OBS exports INTERFACE_COMPILE_OPTIONS into the generated libobs.pc file. Focus on the CMake integration around Threads::Threads and the reported #6746 regression; done means pkg-config --cflags emits valid flags without unevaluated generator expressions and the wlrobs build succeeds.