[build] Fix msan after clang roll.

Port https://codereview.chromium.org/1474923002

BUG=chromium:538614,chromium:559530,chromium:560589
LOG=n
TBR=jochen@chromium.org, thakis@chromium.org, hans@chromium.org,

Review URL: https://codereview.chromium.org/1478863005

Cr-Commit-Position: refs/heads/master@{#32326}

build/standalone.gypi

@@ -575,9 +575,11 @@
                 'cflags': [
                   '-fsanitize=memory',
                   '-fsanitize-memory-track-origins=<(msan_track_origins)',
+                  '-fPIC',
                 ],
                 'ldflags': [
                   '-fsanitize=memory',
+                  '-pie',
                 ],
                 'defines': [
                   'MEMORY_SANITIZER',