Rename V8_SANDBOX to V8_ENABLE_SANDBOX

This change ocurred in V8 at
   https://chromium-review.googlesource.com/c/v8/v8/+/3660251

but PDFium wasn't updated. When built in a non-standalone checkout,
the fuzzers now fail to start with an error:
  # Fatal error in ../../v8/src/init/v8.cc, line 131
  # Check failed: GetProcessWideSandbox()->is_initialized().

since the symbols are mismatched prior to this CL.

Change-Id: If0cbe0725db0768259f9107987aad7da234c6b18
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/94172
Commit-Queue: Nigi <nigi@chromium.org>
Auto-Submit: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Nigi <nigi@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

samples/simple_with_v8.cc

diff --git a/samples/simple_with_v8.cc b/samples/simple_with_v8.cc
index 8b37c72..0bb377a 100644
--- a/samples/simple_with_v8.cc
+++ b/samples/simple_with_v8.cc
@@ -20,7 +20,7 @@
   v8::V8::InitializeExternalStartupData(argv[0]);
   v8::Platform* platform = v8::platform::NewDefaultPlatform().release();
   v8::V8::InitializePlatform(platform);
-#ifdef V8_SANDBOX
+#ifdef V8_ENABLE_SANDBOX
   v8::V8::InitializeSandbox();
 #endif
   v8::V8::Initialize();

testing/v8_initializer.cpp

diff --git a/testing/v8_initializer.cpp b/testing/v8_initializer.cpp
index 5dcb2bd..d789278 100644
--- a/testing/v8_initializer.cpp
+++ b/testing/v8_initializer.cpp
@@ -80,7 +80,7 @@
   static const char kAdditionalV8Flags[] = "--predictable --expose-gc";
   v8::V8::SetFlagsFromString(kAdditionalV8Flags);
 
-#ifdef V8_SANDBOX
+#ifdef V8_ENABLE_SANDBOX
   v8::V8::InitializeSandbox();
 #endif
   v8::V8::Initialize();