(mostly) working wtf / wtf_unittests gn targets

tools/gn/secondary/third_party/libxml/BUILD.gn

Index: tools/gn/secondary/third_party/libxml/BUILD.gn
diff --git a/tools/gn/secondary/third_party/libxml/BUILD.gn b/tools/gn/secondary/third_party/libxml/BUILD.gn
index 2a7a3dea3fbd23e0a589801bcfff7cff237c9fe6..c60c30ece160f44e97b457cf0242d06a8e82e698 100644
--- a/tools/gn/secondary/third_party/libxml/BUILD.gn
+++ b/tools/gn/secondary/third_party/libxml/BUILD.gn
@@ -155,6 +155,14 @@ static_library("libxml2") {
     ldflags = [ "-ldl" ]
   }
 
+  if (is_mac || is_android) {
+    # http://www.xmlsoft.org/threads.html says that this is required

[Nico, 2013/10/02 15:56:30]

Looking at that page, it seems to no longer say that, "starting with 2.4.7".
third_party/libxml/README.chromium claims we're at 2.7.7.

+    # when using libxml from several threads, which can possibly happen
+    # in chrome. On linux, this is picked up by transitivity from
+    # pkg-config output from build/linux/system.gyp.
+    cflags = [ "-D_REENTRANT" ]
+  }
+
   if (is_clang) {
     cflags = [
       # libxml passes `const unsigned char*` through `const char*`.