Teach the top-level git Makefile to use whatever VS compiler
tool chain is installed on the system.
When building git from the command line in a git-sdk BASH
window with MAKE, the shell environment has environment
variables for GCC tools, but not MSVC tools. MSVC bindings
are only avaliable from the various "VcVarsAll.bat" scripts
run by the "Developer Command Prompt" shortcuts.
Add compat/vcbuild/find_vs_env.bat to the Makefile. It
uses the various "VcVarsAll.bat" scripts in a background
Developer Command Prompt process to compute the proper
environment variables and publish them for use by the Makefile.
[jes: fixed typos, used %SystemRoot% instead of C:\WINDOWS]
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>