Revert of GN: support 32-bit x86 builds (patchset #6 id:100001 of https://codereview.chromium.org/2340463008/ )

Reason for revert:
https://build.chromium.org/p/client.skia.compile/builders/Build-Ubuntu-Clang-x86-Debug-GN_Android/builds/304

Original issue's description:
> GN: support 32-bit x86 builds
>
> Take over Ubuntu -x86- bots.
>
> Note the change to Build-Win-MSVC-x86-Release-GN.json, which is not incidental.
> We'll want target_cpu="x86" there too.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2340463008
>
> Committed: https://skia.googlesource.com/skia/+/1949386ae00485ae92dd5608a2614b9dee417542

TBR=jcgregorio@google.com,borenet@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2338173004
diff --git a/BUILD.gn b/BUILD.gn
index 46d4434..05fe350 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -554,26 +554,22 @@
   ]
 }
 
-if (target_cpu == "x64") {
-  # Our bots only have 64-bit libOSMesa installed.
-  # TODO: worth fixing?
-  executable("fiddle") {
-    include_dirs = [ "$target_gen_dir" ]
-    libs = []
-    if (is_linux) {
-      libs += [ "OSMesa" ]
-    }
-
-    sources = [
-      "src/images/SkForceLinking.cpp",
-      "tools/fiddle/draw.cpp",
-      "tools/fiddle/fiddle_main.cpp",
-    ]
-    deps = [
-      ":skia",
-      ":skia.h",
-    ]
+executable("fiddle") {
+  include_dirs = [ "$target_gen_dir" ]
+  libs = []
+  if (is_linux) {
+    libs += [ "OSMesa" ]
   }
+
+  sources = [
+    "src/images/SkForceLinking.cpp",
+    "tools/fiddle/draw.cpp",
+    "tools/fiddle/fiddle_main.cpp",
+  ]
+  deps = [
+    ":skia",
+    ":skia.h",
+  ]
 }
 
 # Targets guarded by skia_enable_tools may use //third_party freely.