mk: Fix Windows cross-build prefix

Author: klutzy

mk/cfg/i686-pc-windows-gnu

@@ -1,5 +1,5 @@
 # i686-pc-windows-gnu configuration
-CROSS_PREFIX_i686-pc-windows-gnu=i686-pc-windows-gnu-
+CROSS_PREFIX_i686-pc-windows-gnu=i686-w64-mingw32-
 CC_i686-pc-windows-gnu=gcc
 CXX_i686-pc-windows-gnu=g++
 CPP_i686-pc-windows-gnu=gcc -E

mk/cfg/x86_64-pc-windows-gnu

@@ -1,5 +1,5 @@
 # x86_64-pc-windows-gnu configuration
-CROSS_PREFIX_x86_64-pc-windows-gnu=x86_64-pc-windows-gnu-
+CROSS_PREFIX_x86_64-pc-windows-gnu=x86_64-w64-mingw32-
 CC_x86_64-pc-windows-gnu=gcc
 CXX_x86_64-pc-windows-gnu=g++
 CPP_x86_64-pc-windows-gnu=gcc -E