Trouble building master with ccache on Windows

Hi there,

I just noticed that, on master, building with ccache on Windows fails
when building any external packages with their own configure. The
configure script would fail to detect C++ compiler. Without ccache, it
builds fine.  Also, even with ccache, the internal modules build just
fine. It's the external packages, such as liblangtag, libwpd etc that
have issues.

Peter, I understand that you've been working on a gcc wrapper for
MSVC. Is it possible that this issue with ccache is somehow related to
that?

Here is how mine is set up.  I have ccacche.exe installed in
/usr/local/bin (in cygwin), and I export

export CC="ccache C:/PROGRA~1/MICROS~1.0/VC/bin/cl.exe"
export CXX="ccache C:/PROGRA~1/MICROS~1.0/VC/bin/cl.exe"

before running autogen.sh, then autogen picks those up for the build.
In my config_host.mk I have

export CC=/usr/local/bin/ccache /cygdrive/c/PROGRA~1/MICROS~1.0/VC/bin/cl.exe
export CC_FOR_BUILD=/usr/local/bin/ccache
/cygdrive/c/PROGRA~1/MICROS~1.0/VC/bin/cl.exe
export CXX=/usr/local/bin/ccache /cygdrive/c/PROGRA~1/MICROS~1.0/VC/bin/cl.exe

Best,

Kohei