Parses pkg-config --cflags output and applies C preprocessor flags to build settings.
All C preprocessor flags (-I, -D, -U, -include, -isystem, -idirafter) are passed
to the D compiler via -P prefix (for DMD/LDC) so they get forwarded to the C preprocessor.
This is called from resolveLibs() which runs after cImportPaths are already processed,
so we add directly to dflags with the -P prefix.
Parses pkg-config --cflags output and applies C preprocessor flags to build settings.
All C preprocessor flags (-I, -D, -U, -include, -isystem, -idirafter) are passed to the D compiler via -P prefix (for DMD/LDC) so they get forwarded to the C preprocessor. This is called from resolveLibs() which runs after cImportPaths are already processed, so we add directly to dflags with the -P prefix.