Set ENABLE_X86_RELAX_RELOCATIONS=NO in clang build script.

The default upstream was recently set to ON, which broke the
linux_upload_clang bot because its binutils is older than 2.26.

Bug: 1113475
Change-Id: Ifcce2f9ab6181e45fe89182dca45dac3b5b10c16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2341369Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Amy Huang <akhuang@google.com>
Cr-Commit-Position: refs/heads/master@{#795567}

tools/clang/scripts/build.py

@@ -541,6 +541,8 @@ def main():
       '-DCOMPILER_RT_USE_LIBCXX=NO',
       # Don't run Go bindings tests; PGO makes them confused.
       '-DLLVM_INCLUDE_GO_TESTS=OFF',
+      # TODO(crbug.com/1113475): Update binutils.
+      '-DENABLE_X86_RELAX_RELOCATIONS=NO',
   ]
 
   if args.gcc_toolchain: