Reland "Move (hopefully) remaining isolate related variables to toolchain.gypi"

gypfiles/standalone.gypi

Index: gypfiles/standalone.gypi
diff --git a/gypfiles/standalone.gypi b/gypfiles/standalone.gypi
index 14533a844f0ac9e76b80b0b4873e8ac70bfb14b8..3191641310d89670860a0079f7cbecf682b7442f 100644
--- a/gypfiles/standalone.gypi
+++ b/gypfiles/standalone.gypi
@@ -112,9 +112,6 @@
       'use_goma%': 0,
       'gomadir%': '',
 
-      # Check if valgrind directories are present.
-      'has_valgrind%': 0,
-
       'test_isolation_mode%': 'noop',
 
       'conditions': [
@@ -164,7 +161,6 @@
     'test_isolation_mode%': '<(test_isolation_mode)',
     'fastbuild%': '<(fastbuild)',
     'coverage%': '<(coverage)',
-    'has_valgrind%': '<(has_valgrind)',
 
     # Add a simple extras solely for the purpose of the cctests
     'v8_extra_library_files': ['../test/cctest/test-extra.js'],