feat(bazel): enable symbolization (#1116)

Symbolization support on Linux and BSD requires link.h which is usually
provided by the GNU C Library (glibc). Assume the header to be present
at all times by unconditionally defining HAVE_SYMBOLIZE on the
corresponding platforms.

bazel/glog.bzl

@@ -91,12 +91,14 @@ def glog_library(with_gflags = 1, **kwargs):
         # Enable declaration of _Unwind_Backtrace
         "-D_GNU_SOURCE",
         "-DHAVE_LINK_H",
+        "-DHAVE_SYMBOLIZE",  # Supported by <link.h>
     ]
 
     linux_only_copts = [
         # For utilities.h.
         "-DHAVE_EXECINFO_H",
         "-DHAVE_LINK_H",
+        "-DHAVE_SYMBOLIZE",  # Supported by <link.h>
     ]
 
     darwin_only_copts = [

src/symbolize.h

@@ -77,6 +77,10 @@
 #  error "symbolize.h" was not included correctly.
 #endif
 
+// We prefer to let the build system detect the availability of certain features
+// such as symbolization support. HAVE_SYMBOLIZE should therefore be defined by
+// the build system in general unless there is a good reason to perform the
+// detection using the preprocessor.
 #ifndef GLOG_NO_SYMBOLIZE_DETECTION
 #  ifndef HAVE_SYMBOLIZE
 // defined by gcc