Major Description
This follow normal standards, and how we do things for other similar dependencies. E.g.
CURL_CONFIG config script used for curl CURL_CFLAGS CFLAGS used for curl CURL_LIBS LIBS used for curl PKG_CONFIG path to pkg-config utility PKG_CONFIG_PATH directories to add to pkg-config's search path PKG_CONFIG_LIBDIR path overriding pkg-config's built-in search path HWLOC_CFLAGS C compiler flags for HWLOC, overriding pkg-config HWLOC_LIBS linker flags for HWLOC, overriding pkg-config SPDYLAY_CFLAGS C compiler flags for SPDYLAY, overriding pkg-config SPDYLAY_LIBS linker flags for SPDYLAY, overriding pkg-config
(before this change the HWLOC prefix was hwloc_, lowercase).