brew install xpra fails while configuring libvpx

[krupan]

I'm trying to brew install xpra on my macbook pro running 10.8.5 and I get this error:

==> ../configure --prefix=/usr/local/Cellar/libvpx/1.2.0 --enable-pic --disable-examples --disable-runtime-cpu-detect --target=x86_64-darwin12-gcc
../configure --prefix=/usr/local/Cellar/libvpx/1.2.0 --enable-pic --disable-examples --disable-runtime-cpu-detect --target=x86_64-darwin12-gcc
Configuring selected codecs
enabling vp8_encoder
enabling vp8_decoder
Configuring for target 'x86_64-darwin12-gcc'
enabling x86_64
enabling mmx
enabling sse
enabling sse2
enabling sse3
enabling ssse3
enabling sse4_1
using yasm
enabling postproc
enabling unit_tests
Unable to invoke compiler: cc -isysroot /Developer/SDKs/MacOSX10.6.sdk -mmacosx-version-min=10.8 -m64 -fomit-frame-pointer -arch x86_64 -O3 -fPIC -Wall -Wdeclaration-after-statement -Wdisabled-optimization -Wpointer-arith -Wtype-limits -Wcast-qual -Wimplicit-function-declaration -Wuninitialized -Wunused-variable -Wunused-but-set-variable -Wno-unused-function

Configuration failed. This could reflect a misconfiguration of your
toolchains, improper options selected, or another problem. If you
don't see any useful error messages above, the next step is to look
at the configure error log file (config.err) to determine what
configure was trying to do when it died.
==> Configuration
HOMEBREW_VERSION: 0.9.5
HEAD: 3ab3c10968ae02796b7101b8147bb67ae3ecfa7d
CPU: 8-core 64-bit ivybridge
OS X: 10.8.5-x86_64
CLT: 4.6.0.0.1.1365549073
X11: 2.7.4 => /opt/X11
==> ENV
HOMEBREW_CC: clang
MAKEFLAGS: -j8
CMAKE_PREFIX_PATH: /usr/local
CMAKE_INCLUDE_PATH: /usr/include/libxml2:/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers
CMAKE_LIBRARY_PATH: /System/Library/Frameworks/OpenGL.framework/Versions/Current/Libraries
PKG_CONFIG_LIBDIR: /usr/lib/pkgconfig:/usr/local/Library/ENV/pkgconfig/10.8
ACLOCAL_PATH: /usr/local/share/aclocal
OBJC: cc
PATH: /usr/local/Library/ENV/4.3:/usr/local/opt/yasm/bin:/usr/bin:/bin:/usr/sbin:/sbin

Error: libvpx did not build