Update escaping in Android.bp files

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.

Soong has been updated to automatically handle ninja and shell
escaping, remove extra escaping from Android.bp files.

Bug: 31221587
Test: m -j
Change-Id: I8bb59f4247be95b33242d855f717004dec379307
diff --git a/Android.bp b/Android.bp
index 82e656c..a0e2e10 100644
--- a/Android.bp
+++ b/Android.bp
@@ -21,7 +21,7 @@
         "-fno-exceptions",
         "-fvisibility=hidden",
         "-Wno-missing-field-initializers",
-        "-DNINJA_PYTHON=\\\"python\\\"",
+        "-DNINJA_PYTHON=\"python\"",
         "-DNINJA_HAVE_BROWSE",
     ],
     target: {