Enable tcmalloc VDSO support only on x86 to reduce static initializers

base/allocator/BUILD.gn

Index: base/allocator/BUILD.gn
diff --git a/base/allocator/BUILD.gn b/base/allocator/BUILD.gn
index c04a0e1417d3900ad2bcccfab2d2b0b6066c2304..9d09a357af6efcaf2d73a551ee46cc1c54409b01 100644
--- a/base/allocator/BUILD.gn
+++ b/base/allocator/BUILD.gn
@@ -118,10 +118,7 @@ if (is_win) {
 
 if (use_allocator == "tcmalloc") {
   # tcmalloc currently won't compile on Android.
-  # TODO(crbug.com/559766) this should be a source_set but
-  # there are static initializers that get accidentally linked
-  # into chrome from vdso_support.cc that need to be addressed first.
-  static_library("tcmalloc") {
+  source_set("tcmalloc") {
     tcmalloc_dir = "//third_party/tcmalloc/chromium"
 
     # Don't check tcmalloc's includes. These files include various files like
@@ -292,4 +289,4 @@ if (use_allocator == "tcmalloc") {
 
     deps += [ "//base/third_party/dynamic_annotations" ]
   }
-}  # !is_android
+}  # use_allocator == "tcmalloc"