Fix conflict with pkgconfig generation

cmake/HPX_GeneratePackageUtils.cmake

@@ -242,16 +242,18 @@ function(hpx_sanitize_usage_requirements property is_build)
 
 endfunction(hpx_sanitize_usage_requirements)
 
-function(hpx_filter_cuda_flags cflag_list)
-  set(_cflag_list "${${cflag_list}}")
-  string(REGEX REPLACE "\\$<\\$<COMPILE_LANGUAGE:CUDA>:[^>]*>;?" "" _cflag_list
-                       "${_cflag_list}"
-  )
-  set(${cflag_list}
-      ${_cflag_list}
-      PARENT_SCOPE
-  )
-endfunction(hpx_filter_cuda_flags)
+function(hpx_filter_language_flags cflag_list)
+    set(_cflag_list "${${cflag_list}}")
+    # We are always in CXX, so replace conditional values with the values themselves
+    string(REGEX REPLACE "\\$<\\$<COMPILE_LANGUAGE:CXX>:([^>]*)>?" "\\1" _cflag_list "${_cflag_list}")
+    # Remove conditional values for other languages
+    string(REGEX REPLACE "\\$<\\$<COMPILE_LANGUAGE:[^>]*>:([^>]*)>?" "" _cflag_list "${_cflag_list}")
+
+    set(${cflag_list}
+        ${_cflag_list}
+        PARENT_SCOPE
+    )
+endfunction(hpx_filter_language_flags)
 
 # Append the corresponding (-D, -I) flags for the compilation
 function(
@@ -383,14 +385,18 @@ function(hpx_generate_pkgconfig_from_target target template is_build)
     hpx_compile_definitions hpx_compile_options hpx_pic_option
     hpx_include_directories hpx_system_include_directories hpx_cflags_list
   )
-  # Cannot generate one file per language yet so filter out cuda
-  hpx_filter_cuda_flags(hpx_cflags_list)
+  # Generator expressions that depend on language must be filtered out
+  hpx_filter_language_flags(hpx_cflags_list)
   hpx_construct_library_list(
     hpx_link_libraries hpx_link_options hpx_library_list
   )
 
   string(TOLOWER ${CMAKE_BUILD_TYPE} build_type)
 
+#   Print hpx_library_list and hpx_cflags_list
+    message(STATUS "hpx_library_list: ${hpx_library_list}")
+    message(STATUS "hpx_cflags_list: ${hpx_cflags_list}")
+
   configure_file(
     cmake/templates/${template}.pc.in
     ${OUTPUT_DIR}${template}_${build_type}.pc.in @ONLY ESCAPE_QUOTES