Fix ANGLE egl.h include for tests.

EGLImageWrappingTests only need to compile against ANGLE's egl.h; they
don't need to link against it.

Also pass the correct filename (libEGL.dylib) on Mac.

Bug: dawn:1284
Change-Id: Iae7eb194263772bd0e92fe53c90d938b26a5735d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/91641
Commit-Queue: Stephen White <senorblanco@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/dawn/tests/BUILD.gn

@@ -598,7 +598,7 @@ source_set("white_box_tests_sources") {
 
   if (dawn_enable_opengles && defined(dawn_angle_dir)) {
     sources += [ "white_box/EGLImageWrappingTests.cpp" ]
-    deps += [ "${dawn_angle_dir}:libEGL" ]
+    include_dirs = [ "${dawn_angle_dir}/include" ]
   }
 
   libs = []

src/dawn/tests/white_box/EGLImageWrappingTests.cpp

@@ -29,8 +29,10 @@ namespace {
 class EGLFunctions {
   public:
     EGLFunctions() {
-#ifdef DAWN_PLATFORM_WINDOWS
+#if defined(DAWN_PLATFORM_WINDOWS)
         const char* eglLib = "libEGL.dll";
+#elif defined(DAWN_PLATFORM_MACOS)
+        const char* eglLib = "libEGL.dylib";
 #else
         const char* eglLib = "libEGL.so";
 #endif