[Vala] why valac says "error: Failed to execute child process (Exec format error)"

[oyster <lepto python gmail com>]

I am using mingw + msys on win7 64bits. The gcc can compile to produce
EXE file, and pkg-config can run no problem

I can compile vala_0.32.0 without problem

but when I try to use "valac -v hello.vala" to compile any vala source, I find
[quote]
Loaded package `E:\msys\opt\windows_32\vala-my-build\share/vala-0.32/vapi/glib-2.0.vapi'
Loaded package `E:\msys\opt\windows_32\vala-my-build\share/vala-0.32/vapi/gobject-2.0.vapi'
error: Failed to execute child process (Exec format error)
...
Compilation failed: 3 error(s), 0 warning(s)
[/quote]

Any hints to find what is the problem? Thanks