fix: fontconfig for linux

Author: Danielku15

build/Build.LibSkia.cs

@@ -215,10 +215,13 @@ partial class Build
                 newSources += "    \"../../wrapper/include/SkFontMgr_alphaskia.h\",\n";
                 newSources += "  ]\n";
                 newSources += "  public = [ \"../../wrapper/include/SkFontMgr_alphaskia.h\" ]";
-                newSources += "  defines = []";
+                newSources += "  defines = []\n";
                 newSources += "  if (is_win) {\n";
                 newSources += "    defines += [ \"ALPHASKIA_FONTMGR_WINDOWS\" ]\n";
                 newSources += "  }\n";
+                newSources += "  if (is_linux) {\n";
+                newSources += "    defines += [ \"ALPHASKIA_FONTMGR_LINUX\" ]\n";
+                newSources += "  }\n";
                 newSources += "  if (is_android) {\n";
                 newSources += "    defines += [ \"ALPHASKIA_FONTMGR_ANDROID\" ]\n";
                 newSources += "  }\n";

wrapper/src/SkFontMgr_alphaskia.cpp

@@ -9,6 +9,9 @@
 #if defined(ALPHASKIA_FONTMGR_WINDOWS)
 #include "../../externals/skia/include/ports/SkTypeface_win.h"
 #define CREATE_OPERATING_SYSTEM_FONTMGR SkFontMgr_New_DirectWrite()
+#elif defined(ALPHASKIA_FONTMGR_LINUX)
+#include "../../externals/skia/include/ports/SkFontMgr_fontconfig.h"
+#define CREATE_OPERATING_SYSTEM_FONTMGR SkFontMgr_New_FontConfig(nullptr)
 #elif defined(ALPHASKIA_FONTMGR_ANDROID)
 #include "../../externals/skia/include/ports/SkFontMgr_android.h"
 #define CREATE_OPERATING_SYSTEM_FONTMGR SkFontMgr_New_Android(nullptr)