contribs: fix cmake target on Windows

On Windows cmake build for a Visual Studio target if it's installed, no matter
what the target we want to build. Reverting to MSys makefiles allow normal
autotools builds to be used

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>

contrib/bootstrap

@@ -247,6 +247,7 @@ test -z "$BUILD_NETWORK" || add_make_enabled "BUILD_NETWORK"
 test -z "$ENABLE_SMALL" || add_make_enabled "ENABLE_SMALL"
 test -z "$GPL" || add_make_enabled "GPL"
 test -z "$WITH_OPTIMIZATION" || add_make_enabled "WITH_OPTIMIZATION"
+test "`uname -o`" != "Msys" || add_make "CMAKE_GENERATOR := -G \"MSYS Makefiles\""
 
 #
 # Checks

contrib/src/main.mak

@@ -363,7 +363,7 @@ endif
 RECONF = mkdir -p -- $(PREFIX)/share/aclocal && \
 	cd $< && $(AUTORECONF) -fiv $(ACLOCAL_AMFLAGS)
 CMAKE = cmake . -DCMAKE_TOOLCHAIN_FILE=$(abspath toolchain.cmake) \
-		-DCMAKE_INSTALL_PREFIX=$(PREFIX)
+		-DCMAKE_INSTALL_PREFIX=$(PREFIX) $(CMAKE_GENERATOR)
 
 #
 # Per-package build rules