Currently, for host builds, pkg-config usage is autodetected based on it's availability in the mkspec or the PATH. For xcompile builds, pkg-config is disabled unless -force-pkg-config is passed. -force-pkg-config is poorly named since it doesn't reflect the fact that it applies only to xplatform builds. It is in fact the only way to enable pkg-config in xcompile builds. And when passed, it doesn't actually force anything since all it does is check env variables. To add to the confusion, it prints a warning even if the env variables are setup correctly. This patch remedies the situation. It adds (-no)-pkg-config. The flag works for both host and xcompile builds. By default, the value is 'auto'. In this mode, it will try try to detect pkg-config from the path. If found, it will be used. For xcompiled builds, we use some heuristics to determine if the pkg-config is actually usable: 1. if -sysroot is not set and the environment variables PKG_CONFIG_LIBDIR or PKG_CONFIG_SYSROOT_DIR are not set, we disable pkg-config. 2. if -sysroot is set, then we setup PKG_CONFIG_LIBDIR and PKG_CONFIG_SYSROOT_DIR automatically (provided $SYSROOT/usr/lib/pkgconfig exists). If the value is 'yes', configure will error if it's heuristics fail to detect a usable pkg-config. If the value is 'no', pkg-config usage is disabled. If the value is 'force', configure will skip it's heuristics and use pkg-config anyway. This mode is useful, for example, when compiling for 32-bit on 64-bit systems. This change also removes references to PKG_CONFIG_SYSROOT (PKG_CONFIG_SYSROOT_DIR is the correct environment variable). Change-Id: I07fc8d48603c65a60de0336fc6276e90fcb41430 Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>