CMake: Add option to link against system-wide Gflags library

It is disabled by default, so should not affect existing configurations.

Main benefits of this goes as:

- Linux distros can use that to avoid libraries duplication and link
  blender package against gflags package from the system.

- It it easier to test whether Blender works with updated version of
  Gflags prior to re-bundling the library.

1 files changed, 12 insertions, 10 deletions

diff --git a/intern/libmv/intern/logging.cc b/intern/libmv/intern/logging.cc
index 77b56ef4df3..9b8adf09a97 100644
--- a/intern/libmv/intern/logging.cc
+++ b/intern/libmv/intern/logging.cc
@@ -29,27 +29,29 @@
 #include "libmv/logging/logging.h"
 
 void libmv_initLogging(const char* argv0) {
+  using LIBMV_GFLAGS_NAMESPACE::SetCommandLineOption;
   // Make it so FATAL messages are always print into console.
   char severity_fatal[32];
   snprintf(severity_fatal, sizeof(severity_fatal), "%d",
            google::GLOG_FATAL);
-
   google::InitGoogleLogging(argv0);
-  gflags::SetCommandLineOption("logtostderr", "1");
-  gflags::SetCommandLineOption("v", "0");
-  gflags::SetCommandLineOption("stderrthreshold", severity_fatal);
-  gflags::SetCommandLineOption("minloglevel", severity_fatal);
+  SetCommandLineOption("logtostderr", "1");
+  SetCommandLineOption("v", "0");
+  SetCommandLineOption("stderrthreshold", severity_fatal);
+  SetCommandLineOption("minloglevel", severity_fatal);
 }
 
 void libmv_startDebugLogging(void) {
-  gflags::SetCommandLineOption("logtostderr", "1");
-  gflags::SetCommandLineOption("v", "2");
-  gflags::SetCommandLineOption("stderrthreshold", "1");
-  gflags::SetCommandLineOption("minloglevel", "0");
+  using LIBMV_GFLAGS_NAMESPACE::SetCommandLineOption;
+  SetCommandLineOption("logtostderr", "1");
+  SetCommandLineOption("v", "2");
+  SetCommandLineOption("stderrthreshold", "1");
+  SetCommandLineOption("minloglevel", "0");
 }
 
 void libmv_setLoggingVerbosity(int verbosity) {
+  using LIBMV_GFLAGS_NAMESPACE::SetCommandLineOption;
   char val[10];
   snprintf(val, sizeof(val), "%d", verbosity);
-  gflags::SetCommandLineOption("v", val);
+  SetCommandLineOption("v", val);
 }