sdk build: use MINGW_ARCH in favor of MINGW_INSTALL (which is deprecated)

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

git-extra/git-sdk.sh

@@ -354,7 +354,7 @@ sdk () {
 			then
 				case "$MSYSTEM" in
 				MSYS) sdk makepkg -f;;
-				MINGW*) MINGW_INSTALLS=${MSYSTEM,,} sdk makepkg-mingw -f;;
+				MINGW*) MINGW_ARCH=${MSYSTEM,,} sdk makepkg-mingw -f;;
 				esac
 				return $?
 			fi