Propagate toolchain-file to external-project (#374)

If defined, propagate the CMAKE_TOOLCHAIN_FILE argument to the cmake
argument of freetype, zlib and ogre projects.

Change-Id: Ibf2802b96c2238a06191e78a1b2a3128769a83af
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>

rviz_ogre_vendor/CMakeLists.txt

@@ -28,6 +28,10 @@ macro(build_freetype)
     list(APPEND extra_cmake_args "-DCMAKE_C_FLAGS=/w")
   endif()
 
+  if(DEFINED CMAKE_TOOLCHAIN_FILE)
+    list(APPEND extra_cmake_args "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}")
+  endif()
+
   include(ExternalProject)
   ExternalProject_Add(freetype-2.8.1
     URL https://git.savannah.gnu.org/cgit/freetype/freetype2.git/snapshot/freetype2-VER-2-6-5.tar.gz
@@ -57,6 +61,10 @@ macro(build_zlib)
     list(APPEND extra_cmake_args "-DCMAKE_C_FLAGS=/w")
   endif()
 
+  if(DEFINED CMAKE_TOOLCHAIN_FILE)
+    list(APPEND extra_cmake_args "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}")
+  endif()
+
   include(ExternalProject)
   ExternalProject_Add(zlib-1.2.11
     URL https://www.zlib.net/fossils/zlib-1.2.11.tar.gz
@@ -120,6 +128,10 @@ macro(build_ogre)
     set(patch_exe patch)
   endif()
 
+  if(DEFINED CMAKE_TOOLCHAIN_FILE)
+    list(APPEND extra_cmake_args "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}")
+  endif()
+
   include(ExternalProject)
   ExternalProject_Add(ogre-master-ca665a6
     URL https://github.com/OGRECave/ogre/archive/v1.10.11.zip