Opal has a dependency on liblcms1-dev.
If gnustep-config is newly installed and not in path, add it to path BEFORE the first use.
Fixed lack of CFLAGS and LD_LIBRARY_PATH that includes our build of libobjc2 in case libobjc2 was already installed.
Cleaned up the way we test with WITH_CLEAN. Used string comparison so we don't run into 'integer expected' issues with bash.
Fixed lack of gnustep-config in PATH breaking the build.