build debug on linux for gdb

Building with this define enables additional
checks for standard library functions when
running gdb, and allows printing std::string.

R=halcanary@google.com

Bug: skia:
Change-Id: Ib71c179d8cbacbcd7f17a1c85f912072918e6be8
Reviewed-on: https://skia-review.googlesource.com/140786
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
1 file changed