clang/win: Let SK_TRACEHR not produce -Wunused-value warnings in release builds.
clang/win: Let SK_TRACEHR not produce -Wunused-value warnings in release builds.

Fixes warnings like:
..\..\third_party\skia\include\utils\win\SkHRESULT.h(51,23) :  note: expanded from macro 'HRNM'
                      ^~~~~~~~~~~~~~~~~~~~~~~~~
..\..\third_party\skia\include\utils\win\SkHRESULT.h(26,20) :  note: expanded from macro 'HR_GENERAL'
        SK_TRACEHR(_hr, _msg);\
                   ^~~
..\..\third_party\skia\include\utils\win\SkHRESULT.h(20,31) :  note: expanded from macro 'SK_TRACEHR'
                              ^~~

BUG=chromium:505318
TBR=reed
This is a trivial implementation change.

Review URL: https://codereview.chromium.org/1503463004

tmpvar/skia.cc,rubenvb/skia,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,qrealka/skia-hc,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,qrealka/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,tmpvar/skia.cc,HalCanary/skia-hc,tmpvar/skia.cc,HalCanary/skia-hc,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,tmpvar/skia.cc,HalCanary/skia-hc,google/skia,tmpvar/skia.cc,aosp-mirror/platform_external_skia,qrealka/skia-hc,rubenvb/skia,HalCanary/skia-hc,qrealka/skia-hc,google/skia,aosp-mirror/platform_external_skia,qrealka/skia-hc,rubenvb/skia,tmpvar/skia.cc,google/skia,HalCanary/skia-hc,tmpvar/skia.cc,aosp-mirror/platform_external_skia,qrealka/skia-hc,qrealka/skia-hc,HalCanary/skia-hc,rubenvb/skia,google/skia,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,tmpvar/skia.cc,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,rubenvb/skia,tmpvar/skia.cc,google/skia,Hikari-no-Tenshi/android_external_skia,qrealka/skia-hc,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia