Use "SmileyHack" to inject CMake vars to get the right output suffix.

This fixes known issues with output binary suffix in the custom emscripten.toolchain.cmake and FindUrho3D.cmake modules.

CMake/Modules/FindUrho3D.cmake

@@ -236,6 +236,7 @@ else ()
                 endif ()
             endif ()
             set (COMPILER_FLAGS "${COMPILER_32BIT_FLAG} ${CMAKE_REQUIRED_FLAGS}")
+            string (REPLACE .js ";" COMPILER_FLAGS "${COMPILER_FLAGS}")     # Emscripten-specific - revise SmileyHack to inject empty suffix to keep try_compile() happy
             # FIXME: For yet an unknown reason, CMake seems to fail to setup the sysroot as expected here, so we have to set it manually
             if (ANDROID)
                 set (COMPILER_FLAGS "${COMPILER_FLAGS} --sysroot=\"${CMAKE_SYSROOT}\"")

CMake/Modules/UrhoCommon.cmake

@@ -627,10 +627,6 @@ else ()
                 endif ()
                 set (CMAKE_C_FLAGS_RELEASE "-Oz -DNDEBUG")
                 set (CMAKE_CXX_FLAGS_RELEASE "-Oz -DNDEBUG")
-                # CMake does not treat Emscripten as a valid platform yet, certain platform-specific variables cannot be set in the
-                # toolchain file as they get overwritten by CMake internally as per Linux platform default, so set them here for now
-                set (CMAKE_EXECUTABLE_SUFFIX_C .html)
-                set (CMAKE_EXECUTABLE_SUFFIX_CXX .html)
                 # Linker flags
                 if (EMSCRIPTEN_ALLOW_MEMORY_GROWTH)
                     set (MEMORY_LINKER_FLAGS "-s ALLOW_MEMORY_GROWTH=1")

CMake/Toolchains/emscripten.toolchain.cmake

@@ -138,14 +138,15 @@ foreach (LANG C CXX)
     # The ABI info could not be checked as per normal as CMake does not understand the test build output from Emscripten, so bypass it also
     set (CMAKE_${LANG}_ABI_COMPILED TRUE)
     set (CMAKE_${LANG}_SIZEOF_DATA_PTR 4)   # Assume it is always 32-bit for now (we could have used our CheckCompilerToolChains.cmake module here)
-    # There could be a bug in CMake itself where setting CMAKE_EXECUTABLE_SUFFIX variable outside of the scope, where it processes the platform configuration files, does not being honored by try_compile() command and as a result all the check macros that depend on try_compile() do not work properly when the CMAKE_EXECUTABLE_SUFFIX variable is only being set later further down the road; At least one of the CMake devs has the opinion that this is the intended behavior but it is an unconvincing explanation because setting CMAKE_EXECUTABLE_SUFFIX variable later does have the desired effect everywhere else EXCEPT the try_compile() command
-    # We are forced to set CMAKE_EXECUTABLE_SUFFIX_C and CMAKE_EXECUTABLE_SUFFIX_CXX here as a workaround; we could not just set CMAKE_EXECUTABLE_SUFFIX directly because CMake processes platform configuration files after the toolchain file and since we tell CMake that we are cross-compiling for 'Linux' platform via CMAKE_SYSTEM_NAME variable, CMake initializes the CMAKE_EXECUTABLE_SUFFIX to empty string (as expected for Linux platform); the workaround avoids our setting from being overwritten by platform configuration files by using the C and CXX language variants of the variable
-    # The executable suffix needs to be .js for the below Emscripten-specific compiler setting to be effective
-    set (CMAKE_EXECUTABLE_SUFFIX_${LANG} .js)
+    # We could not set CMAKE_EXECUTABLE_SUFFIX directly because CMake processes platform configuration files after the toolchain file and since we tell CMake that we are cross-compiling for 'Linux' platform (Emscripten is not a valid platform yet in CMake) via CMAKE_SYSTEM_NAME variable, as such CMake force initializes the CMAKE_EXECUTABLE_SUFFIX to empty string (as expected for Linux platform); To workaround it we have to use CMAKE_EXECUTABLE_SUFFIX_C and CMAKE_EXECUTABLE_SUFFIX_CXX instead, which are fortunately not being touched by platform configuration files
+    if (NOT DEFINED CMAKE_EXECUTABLE_SUFFIX_${LANG})
+        set (CMAKE_EXECUTABLE_SUFFIX_${LANG} .html)
+    endif ()
 endforeach ()
 
-# Set required compiler flags for internal CMake various check_xxx() macros which rely on the error to occur for the check to be performed correctly
-set (CMAKE_REQUIRED_FLAGS "-s ERROR_ON_UNDEFINED_SYMBOLS=1")
+# Set required compiler flags for various internal CMake checks which rely on the compiler/linker error to be occured for the check to be performed correctly
+# The executable suffix needs to be .js for the below Emscripten-specific compiler setting to be effective
+set (CMAKE_REQUIRED_FLAGS "-s ERROR_ON_UNDEFINED_SYMBOLS=1;-DSmileyHack=byYaoWT;-DCMAKE_EXECUTABLE_SUFFIX_C=.js;-DCMAKE_EXECUTABLE_SUFFIX_CXX=.js")
 
 # Use response files on Windows host
 if (CMAKE_HOST_WIN32)