external_deps: don't munge SDL config

The build script for mingw sdl2 uses prebuilt binaries, but calls a
makefile which only substitutes some hard-coded paths into some build
config helpers and copies the files. Just copy the files ourselves and
don't munge the configs: the unmunged cmake uses a relative path
which is actually what we want. In newer SDL versions the makefile munges the
cmake configs (in addition to the shell-based one) which breaks us.

Author: slipher

external_deps/build.sh

@@ -341,7 +341,7 @@ build_sdl2() {
 	case "${PLATFORM}" in
 	windows-*-mingw)
 		cd "${dir_name}"
-		make install-package arch="${HOST}" prefix="${PREFIX}"
+		cp -rv "${HOST}"/* "${PREFIX}/"
 		;;
 	windows-*-msvc)
 		cd "${dir_name}"