Allow asmjs builds to use core/fxge/fx_ge_linux.cpp.

While some of the font path options in fx_ge_linux.cpp may not be useful
to asmjs builds, the code in CFX_LinuxFontInfo::MapFont() may still be
relevant. As such, relax the check that fx_ge_linux.cpp is Linux only.

Change-Id: I8e6dd518f371623297330efc51f43740d5e4837f
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/71332
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

core/fxge/fx_ge_linux.cpp

diff --git a/core/fxge/fx_ge_linux.cpp b/core/fxge/fx_ge_linux.cpp
index 6e39c75..8fcc921 100644
--- a/core/fxge/fx_ge_linux.cpp
+++ b/core/fxge/fx_ge_linux.cpp
@@ -16,7 +16,7 @@
 #include "core/fxge/systemfontinfo_iface.h"
 #include "third_party/base/stl_util.h"
 
-#if !defined(OS_LINUX)
+#if !defined(OS_LINUX) && !defined(OS_ASMJS)
 #error "Included on the wrong platform"
 #endif