Help: Fix unescaped asterisks in docs for SKIP_PRECOMPILE_HEADERS

Help/prop_sf/SKIP_PRECOMPILE_HEADERS.rst

@@ -6,8 +6,8 @@ Is this source file skipped by :prop_tgt:`PRECOMPILE_HEADERS` feature.
 This property helps with build problems that one would run into
 when using the :prop_tgt:`PRECOMPILE_HEADERS` feature.
 
-One example would be the usage of Objective-C (*.m) files, and
-Objective-C++ (*.mm) files, which lead to compilation failure
+One example would be the usage of Objective-C (``*.m``) files, and
+Objective-C++ (``*.mm``) files, which lead to compilation failure
 because they are treated (in case of Ninja / Makefile generator)
 as C, and CXX respectively. The precompile headers are not
 compatible between languages.