Remove the default setting for clcompile_cmd in msvs-ninja
Remove the default setting for clcompile_cmd in msvs-ninja

The 'msvs_external_builder_clcompile_cmd' logic is preserved, this commit
simply removes the default setting.  It can be restored by individual
developers based on personal preference.

BUG=352876
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/246613003
witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp