Makefile: fix build if CC/CXX not set in env

this should also hopefully make the CI/CD work again

Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>

Makefile

@@ -108,7 +108,7 @@ PKGFILES = $(shell find pkg -type f -name '*.go')
 endif
 
 lib/%.a: $(PKGFILES)
-	@XBUILD=no MAKE=${MAKE} ./gui/build.sh --just-golib
+	@XBUILD=no CC=${CC} CXX=${CXX} MAKE=${MAKE} ./gui/build.sh --just-golib
 
 relink_vendor:
 	@echo "============RELINK VENDOR============="
@@ -140,7 +140,7 @@ build_gui: build_golib relink_vendor
 	@echo "==============BUILD GUI==============="
 	@echo "TARGET: ${TARGET}"
 	@echo "VENDOR_PATH: ${VENDOR_PATH}"
-	@XBUILD=no MAKE=${MAKE} QMAKE=${QMAKE} LRELEASE=${LRELEASE} TARGET=${TARGET} VENDOR_PATH=${VENDOR_PATH} APPNAME=${APPNAME} gui/build.sh --skip-golib
+	@XBUILD=no CC=${CC} CXX=${CXX} MAKE=${MAKE} QMAKE=${QMAKE} LRELEASE=${LRELEASE} TARGET=${TARGET} VENDOR_PATH=${VENDOR_PATH} APPNAME=${APPNAME} gui/build.sh --skip-golib
 	@echo "============BUILD GUI================="
 
 build: build_helper build_gui