Specify correct /SUBSYSTEM for test_process.exe

test_process.exe was being linked with /SUBSYSTEM:CONSOLE, despite being
a windowed app with a wWinMain entry point. With lld-link.exe this seems
to work fine, suggesting that lld ignores the/SUBSYSTEM flag. lld-link
may change this behavior (https://bugs.llvm.org/show_bug.cgi?id=38397)
so it seems worthwhile to fix the build flags for this executable. Doing
so will also be less confusing.

Bug: 869503
Change-Id: I52a61aab678fa135f3da8c10bc82a4cdf649b5ae
Reviewed-on: https://chromium-review.googlesource.com/1157656
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Chris Sharp <csharp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580616}

chrome/chrome_cleaner/test/BUILD.gn

@@ -184,6 +184,10 @@ executable("test_process") {
     "//chrome/chrome_cleaner/engines:resources",
     "//chrome/chrome_cleaner/os:common_os",
   ]
+
+  # Default entrypoint is main, console app. Change it to wWinMain, windowed.
+  configs -= [ "//build/config/win:console" ]
+  configs += [ "//build/config/win:windowed" ]
 }
 
 executable("test_service") {