Provide MAGNUM_TARGET_WEBGL also in CMake.

doc/cmake.dox

@@ -167,6 +167,7 @@ are also available as preprocessor variables if including @ref Magnum/Magnum.h:
 -   `MAGNUM_TARGET_GLES3` -- Defined if compiled for OpenGL ES 3.0
 -   `MAGNUM_TARGET_DESKTOP_GLES` -- Defined if compiled with OpenGL ES
     emulation on desktop OpenGL
+-   `MAGNUM_TARGET_WEBGL` --- Defined if compiled for WebGL
 
 If `MAGNUM_BUILD_DEPRECATED` is defined, the `MAGNUM_INCLUDE_DIR` variable also
 contains path directly to Magnum directory (i.e. for includes without `Magnum/`

modules/FindMagnum.cmake

@@ -92,6 +92,7 @@
 #  MAGNUM_TARGET_GLES3          - Defined if compiled for OpenGL ES 3.0
 #  MAGNUM_TARGET_DESKTOP_GLES   - Defined if compiled with OpenGL ES
 #   emulation on desktop OpenGL
+#  MAGNUM_TARGET_WEBGL          - Defined if compiled for WebGL
 #
 # If `MAGNUM_BUILD_DEPRECATED` is defined, the `MAGNUM_INCLUDE_DIR` variable
 # also contains path directly to Magnum directory (i.e. for includes without
@@ -207,6 +208,10 @@ string(FIND "${_magnumConfigure}" "#define MAGNUM_TARGET_DESKTOP_GLES" _TARGET_D
 if(NOT _TARGET_DESKTOP_GLES EQUAL -1)
     set(MAGNUM_TARGET_DESKTOP_GLES 1)
 endif()
+string(FIND "${_magnumConfigure}" "#define MAGNUM_TARGET_WEBGL" _TARGET_WEBGL)
+if(NOT _TARGET_WEBGL EQUAL -1)
+    set(MAGNUM_TARGET_WEBGL 1)
+endif()
 
 # Dependent libraries and includes
 set(MAGNUM_INCLUDE_DIRS ${MAGNUM_INCLUDE_DIR}