Don't define BORINGSSL_SHARED_LIBRARY in generated bzl file.

https://boringssl-review.googlesource.com/c/12360/ made us define
BORINGSSL_SHARED_LIBRARY when building tests via Bazel. The test has now
been moved to crypto_test, where the flags are more easily under the
control of the consumer.

Change-Id: If237efca219a1f03d64dc801cc1d585556bf2d1d
Reviewed-on: https://boringssl-review.googlesource.com/16987
Reviewed-by: David Benjamin <davidben@google.com>

util/generate_build_files.py

diff --git a/util/generate_build_files.py b/util/generate_build_files.py
index fabef67..38d757b 100644
--- a/util/generate_build_files.py
+++ b/util/generate_build_files.py
@@ -301,7 +301,7 @@
               out.write('          "%s",\n' % arg)
           out.write('      ],\n')
 
-        out.write('      copts = copts + ["-DBORINGSSL_SHARED_LIBRARY"],\n')
+        out.write('      copts = copts,\n')
 
         if len(data_files) > 0:
           out.write('      data = [\n')