Make build setup a little more Windows-friendly (#4435)

* [build][CMake] Use `find_package(Git)` to confirm existence before trying to use git for version stamp; Use friendlier detection of grep executable on Windows; Use "del" on Windows instead of "rm".

* [build][Windows] Include dirent and msinttypes headers in source tree.

* Remove grep dependency for lua exports generation

* Sneaky pythons hiding in code.

* [build] Change `git_id` macro to skip check if no git directory is present, also now fails gracefully; Fix `today` macro on Windows; Report git revision; Make sure QtSvg module is found.

radio/util/luaexport.py

@@ -75,6 +75,9 @@ with open(inputFile, "r") as inp:
         line = line.strip()
         # print "line: %s"    % line
 
+        if line.find('LEXP') < 0:
+            continue
+
         parts = line.split('LEXP')
         # print parts
         if len(parts) != 2: