Fix for Chromium linux official build

Bug chromium:691427

The official build uses the LLVM gold linker, which seems
to have an issue with some visibility settings. Restoring
these settings for now to solve the issue.

Change-Id: I4f448c38bb7c964b2a53d19e064ecb23c119ab61
Reviewed-on: https://swiftshader-review.googlesource.com/8770
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>

BUILD.gn

diff --git a/BUILD.gn b/BUILD.gn
index b8f17d6..d646afe 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -35,7 +35,6 @@
       "-std=c++11",
       "-Wall",
       "-fexceptions",
-      "-fvisibility=protected",
       "-fno-operator-names",
       "-D__STDC_CONSTANT_MACROS",
       "-D__STDC_LIMIT_MACROS",

src/OpenGL/libGLESv2/BUILD.gn

diff --git a/src/OpenGL/libGLESv2/BUILD.gn b/src/OpenGL/libGLESv2/BUILD.gn
index 3862e8b..cf9d1db 100644
--- a/src/OpenGL/libGLESv2/BUILD.gn
+++ b/src/OpenGL/libGLESv2/BUILD.gn
@@ -41,7 +41,7 @@
     ]
 
     if (is_linux) {
-      cflags += [ "-DGL_APICALL=__attribute__((visibility(\"protected\")))" ]
+      cflags += [ "-DGL_APICALL=" ]
     } else {
       cflags += [ "-DGL_APICALL=__attribute__((visibility(\"default\")))" ]
     }