Let llvm-config --system-libs print full paths if we use them

[aaronpuchert]

Summary

CMake's find_package produces full paths even if we could rely on the
linker to find the library in the standard search path. In that case
perhaps llvm-config --system-libs should reflect this and also use
full paths to mirror the link command that we're using.

This could be an issue for distributors, if they build with libraries in
some local path, but expect users to have them in their standard search
path.

Fixes an issue raised in D132799, since we're now using the same list
for linking libLLVM.

As an alternative, we could produce two different lists, one with just
stems for llvm-config and another with (possibly) full paths for
linking libLLVM.

[aaronpuchert]

No longer needed as we went with a different solution in D132799.

llvm/cmake/modules/GetLibraryName.cmake

-# Returns library name for a given path.
-function(get_library_name path name)
-  get_filename_component(path ${path} NAME)
-  set(prefixes ${CMAKE_FIND_LIBRARY_PREFIXES})
-  set(suffixes ${CMAKE_FIND_LIBRARY_SUFFIXES})
-  list(FILTER prefixes EXCLUDE REGEX "^\\s*$")
-  list(FILTER suffixes EXCLUDE REGEX "^\\s*$")
-  if(prefixes)
-    string(REPLACE ";" "|" prefixes "${prefixes}")
-    string(REGEX REPLACE "^(${prefixes})" "" path ${path})
-  endif()
-  if(suffixes)
-    string(REPLACE ";" "|" suffixes "${suffixes}")
-    string(REGEX REPLACE "(${suffixes})$" "" path ${path})
-  endif()
-  set(${name} "${path}" PARENT_SCOPE)
-endfunction()

llvm/lib/Support/CMakeLists.txt

if(LLVM_ENABLE_ZLIB)
   # CMAKE_BUILD_TYPE is only meaningful to single-configuration generators.
   if(CMAKE_BUILD_TYPE)
     string(TOUPPER ${CMAKE_BUILD_TYPE} build_type)
     get_property(zlib_library TARGET ZLIB::ZLIB PROPERTY LOCATION_${build_type})
   endif()
   if(NOT zlib_library)
     get_property(zlib_library TARGET ZLIB::ZLIB PROPERTY LOCATION)
   endif()
-  get_library_name(${zlib_library} zlib_library)
   set(llvm_system_libs ${llvm_system_libs} "${zlib_library}")
 endif()
 
 if(LLVM_ENABLE_ZSTD)
   # CMAKE_BUILD_TYPE is only meaningful to single-configuration generators.
   if(CMAKE_BUILD_TYPE)
     string(TOUPPER ${CMAKE_BUILD_TYPE} build_type)
     get_property(zstd_library TARGET ${zstd_target} PROPERTY LOCATION_${build_type})
   endif()
   if(NOT zstd_library)
     get_property(zstd_library TARGET ${zstd_target} PROPERTY LOCATION)
   endif()
-  get_library_name(${zstd_library} zstd_library)
   set(llvm_system_libs ${llvm_system_libs} "${zstd_library}")
 endif()
 
 if(LLVM_ENABLE_TERMINFO)
   if(NOT terminfo_library)
     get_property(terminfo_library TARGET Terminfo::terminfo PROPERTY LOCATION)
   endif()
-  get_library_name(${terminfo_library} terminfo_library)
   set(llvm_system_libs ${llvm_system_libs} "${terminfo_library}")
 endif()
 
 set_property(TARGET LLVMSupport PROPERTY LLVM_SYSTEM_LIBS "${llvm_system_libs}")
 
 
 if(LLVM_INTEGRATED_CRT_ALLOC)
   if(LLVM_INTEGRATED_CRT_ALLOC MATCHES "snmalloc$")

llvm/lib/WindowsManifest/CMakeLists.txt

if(LLVM_ENABLE_LIBXML2)
   # CMAKE_BUILD_TYPE is only meaningful to single-configuration generators.
   if(CMAKE_BUILD_TYPE)
     string(TOUPPER ${CMAKE_BUILD_TYPE} build_type)
     get_property(libxml2_library TARGET LibXml2::LibXml2 PROPERTY LOCATION_${build_type})
   endif()
   if(NOT libxml2_library)
     get_property(libxml2_library TARGET LibXml2::LibXml2 PROPERTY LOCATION)
   endif()
-  get_library_name(${libxml2_library} libxml2_library)
   set_property(TARGET LLVMWindowsManifest PROPERTY LLVM_SYSTEM_LIBS ${libxml2_library})
 endif()