Strings like cflags in Android.bp files are parsed by blueprint,
written to build.ninja files, parsed by ninja, and then passed to
/bin/sh -c. This had resulted in a combination of blueprint
(\"), ninja ($$), and shell (\$) escaping being necessary.
Update Soong to automatically handle ninja and shell escaping in
cflags and ldflags.
Bug: 31221587
Test: m -j
Change-Id: Ibe087b2788b355b73c3225b5928870619a0a53bc