Update Win32/Win64 build scripts

dist-build/Makefile.am

@@ -5,5 +5,5 @@ EXTRA_DIST = \
 	android-x86.sh \
 	android-mips.sh \
 	ios.sh \
-	msys-win32.sh \
-	msys-win64.sh
+	msys2-win32.sh \
+	msys2-win64.sh

dist-build/msys-win32.sh

@@ -1,9 +0,0 @@
-#! /bin/sh
-
-export CFLAGS="-O3 -fomit-frame-pointer -march=pentium2 -mtune=nocona"
-export PREFIX="$(pwd)/libsodium-win32"
-
-./configure --prefix="$PREFIX" --exec-prefix="$PREFIX" && \
-make && \
-make check && \
-make install

dist-build/msys2-win32.sh

@@ -0,0 +1,10 @@
+#! /bin/sh
+
+export CFLAGS="-O3 -fomit-frame-pointer -m32 -march=pentium2 -mtune=nocona"
+export PREFIX="$(pwd)/libsodium-win32"
+
+./configure --prefix="$PREFIX" --exec-prefix="$PREFIX" \
+            --host=i686-w64-mingw32 && \
+make && \
+make check && \
+make install

dist-build/msys2-win64.sh

@@ -1,6 +1,6 @@
 #! /bin/sh
 
-export CFLAGS="-O3 -fomit-frame-pointer -m64"
+export CFLAGS="-O3 -fomit-frame-pointer -m64 -march=pentium2 -mtune=nocona"
 export PREFIX="$(pwd)/libsodium-win64"
 
 ./configure --prefix="$PREFIX" --exec-prefix="$PREFIX" \