3fd425aed7 switched write_git_sha1_h_file() in src/SConscript from Popen()ing 'git' directly to using a sh script. Since sh isn't available on Windows the function fails to create the git_sha1.h file and eventually breaks the build when things like src\mesa\main\version.c try to #include it. I'm using the mesa-17.2.4 tag (a4b72e2643) with the VS2015 toolchain.
Reverting write_git_sha1_h_file() to the pre-3fd425aed7 code fixes the build for me.
Please try the latest code. This was fixed back in August. Re-open this bug if you still have trouble.
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