Add note on GCC compiler flags

Add a note on GCC compiler flags

-A needs an assertion
-B needs a argument
-D needs a macro name (Defines a macro with the specified name)
-F needs a path (Specifies a directory to search for header files)
-I needs a path ( Adds a directory to the list of directories to be searched for header files during preprocessing )
-J needs an argument
-L needs an argument (specifies the linking directory) (specify a directory to search for libraries during the linking phase)
-R needs an argument
-T needs an argument
-U needs a macro name (This flag is used to undefine a macro)
-d needs an argument
-e needs an argument
-g includes debug symbols
-h needs an argument
-l (lower case I) needs an argument
-o needs a file name (specifies the output files)
-l (lower case L) needs and argument (This flag is used to link against a specific library)
-u needs an argument (used in symbol linking)
-v is verbose?
-x needs an argument (used to specify the language of the input files)
-z needs an argument

Needs moar research.