build: Remove absolute path on pkg-config

This allows it to be found on macOS and should fix linking libnfs with builds of the Android app

Author: DDRBoxman

build/pkg-config.sh

@@ -10,4 +10,4 @@ ROOT=`dirname "$BIN"`
 export PKG_CONFIG_DIR=
 export PKG_CONFIG_LIBDIR="${ROOT}/lib/pkgconfig:${ROOT}/share/pkgconfig"
 
-exec /usr/bin/pkg-config "$@"
+exec pkg-config "$@"