CMake: prevent mismatched package name warnings

Use all caps for the packages.

Closes https://github.com/wxWidgets/wxWidgets/pull/1886

build/cmake/modules/FindFONTCONFIG.cmake

@@ -0,0 +1,30 @@
+# - Try to find Fontconfig
+# Once done this will define
+#
+#  FONTCONFIG_FOUND - system has Fontconfig
+#  FONTCONFIG_INCLUDE_DIRS - The include directory to use for the Fontconfig headers
+#  FONTCONFIG_LIBRARIES - Link these to use Fontconfig
+
+find_package(PkgConfig)
+pkg_check_modules(PC_FONTCONFIG QUIET fontconfig)
+
+find_path(FONTCONFIG_INCLUDE_DIRS
+    NAMES fontconfig.h
+    HINTS ${PC_FONTCONFIG_INCLUDEDIR}
+          ${PC_FONTCONFIG_INCLUDE_DIRS}
+    PATH_SUFFIXES fontconfig
+)
+
+find_library(FONTCONFIG_LIBRARIES
+    NAMES fontconfig
+    HINTS ${PC_FONTCONFIG_LIBDIR}
+          ${PC_FONTCONFIG_LIBRARY_DIRS}
+)
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(FONTCONFIG DEFAULT_MSG FONTCONFIG_INCLUDE_DIRS FONTCONFIG_LIBRARIES)
+
+mark_as_advanced(
+    FONTCONFIG_INCLUDE_DIRS
+    FONTCONFIG_LIBRARIES
+)