do not hardcode -I/usr/include32 when cross-compiling

When we cross-compile, we do not want any /usr/include paths as that will
conflict with our own system headers.  Disable the hardcoded path when we
have an active sysroot.

BUG=chromium:488360

Review URL: https://codereview.chromium.org/1132853010

Cr-Commit-Position: refs/heads/master@{#330514}

build/common.gypi

@@ -3864,7 +3864,7 @@
                   # and make sure a 32-bit-on-64-bit build picks up the
                   # right files.
                   # For android build, use NDK headers instead of host headers
-                  ['host_arch!="ia32" and OS!="android"', {
+                  ['host_arch!="ia32" and OS!="android" and use_sysroot!=1', {
                     'include_dirs+': [
                       '/usr/include32',
                     ],