xbps-src: create a <cross-target>-pkg-config wrapper when cross compiling.

This wrapper sets the env vars required for proper cross compiling, rather
than always setting them.

common/environment/configure/pkg-config.sh

@@ -6,10 +6,4 @@ if [ -z "$CHROOT_READY" ]; then
 	PKG_CONFIG_PATH="${XBPS_MASTERDIR}/usr/lib/pkgconfig:${XBPS_MASTERDIR}/usr/share/pkgconfig"
 fi
 
-if [ "$CROSS_BUILD" ]; then
-	PKG_CONFIG_SYSROOT_DIR="$XBPS_CROSS_BASE"
-	PKG_CONFIG_PATH="$XBPS_CROSS_BASE/lib/pkgconfig:$XBPS_CROSS_BASE/usr/share/pkgconfig"
-	PKG_CONFIG_LIBDIR="$XBPS_CROSS_BASE/lib/pkgconfig"
-fi
-
 set +a