Add GN assert to prevent GOMA from being used with static analyzer.

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index 6102c8dd91edb56d65979c723d6d8af0306a2f23..b31980668d89732523e9765f83e2e24f7caf1a4d 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -489,6 +489,10 @@ template("clang_toolchain") {
     ld = cxx
 
     if (use_clang_static_analyzer) {
+      # Static analysis isn't supported under GOMA. See crbug.com/687245
+      # for progress on this issue.
+      assert(!use_goma, "'use_clang_static_analyzer' cannot be used with GOMA.")
+
       # Call "ccc-analyzer" or "c++-analyzer" instead of directly calling Clang.
       # |wrapper_tool| sets the environment variables which are read by the
       # analyzer tools.