Make pdfium_embeddertests link in debug component builds.

Target v8 has:

          'direct_dependent_settings': {
            'defines': [
              'V8_SHARED',
              'USING_V8_SHARED',
            ],
          },

For this to work, targets using v8 headers have to depend on v8
directly, else the V8_EXPORT macro won't work. Add a direct
dependency on v8.

BUG=none
TEST=do a debug component build of pdfium_embeddertests on Win,
should work without linker errors

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1349843002 .
diff --git a/BUILD.gn b/BUILD.gn
index 17276e0..bba4818 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -776,6 +776,7 @@
   deps = [
     "//testing/gmock",
     "//testing/gtest",
+    "//v8",
     "//v8:v8_libplatform",
     ":pdfium",
   ]
diff --git a/pdfium.gyp b/pdfium.gyp
index 5c8799e..12314d7 100644
--- a/pdfium.gyp
+++ b/pdfium.gyp
@@ -731,6 +731,7 @@
       'dependencies': [
         '<(DEPTH)/testing/gmock.gyp:gmock',
         '<(DEPTH)/testing/gtest.gyp:gtest',
+        '<(DEPTH)/v8/tools/gyp/v8.gyp:v8',
         '<(DEPTH)/v8/tools/gyp/v8.gyp:v8_libplatform',
         'pdfium',
       ],