Remove now unnecessary msvs_cygwin_shell:1

Was necessary for VS builds, but not with ninja-only.

BUG=123026
TBR=jam@chromium.org
TEST=remove out\Debug\xinput1_3.dll and ninja -C out\Debug xinput1_3.dll

Review URL: https://codereview.chromium.org/132473010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245793 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245793