osgeo4w: build fixes (#137)

restructure and stabilize osgeo4w/msys2 based winGRASS build procedure, provided by and thanks to @jef-n 

* osgeo4w: build fixes
* use cmd //c instead of cmd /c
* osgeo4w: use proj_i instead of proj
* avoid ol msys
* drop -j4
* Use osgeo4w's sqlite

lib/python/ctypes/ctypesgencore/processor/operations.py

@@ -204,7 +204,7 @@ def find_source_libraries(data, opts):
     for library_name in opts.libraries:
         try:
             library = ctypesgencore.libraryloader.load_library(library_name)
-        except ImportError as e:
+        except (ImportError,OSError) as e:
             warning_message("Could not load library \"%s\". Okay, I'll "
                             "try to load it at runtime instead. " % (library_name),
                             cls='missing-library')

mswindows/osgeo4w/env.bat.tmpl

@@ -2,6 +2,8 @@ REM
 REM Environmental variables for GRASS OSGeo4W installer
 REM
 
+call %OSGEO4W_ROOT%\bin\py3_env.bat
+
 set GISBASE=%OSGEO4W_ROOT%\apps\grass\grass@POSTFIX@
 
 REM Uncomment if you want to use Bash instead of Cmd

mswindows/osgeo4w/envdiff.sed

@@ -0,0 +1,14 @@
+/^+++/d;
+/^[^+]/d;
+s/^+//;
+s/\\/\\\\/g;
+/^PATH=/ {
+	s/\\\\/\//g;
+	s#\([=;]\)\([a-zA-Z]\):#\1/\2#g;
+	s/;/:/g;
+}
+s/;/\\;/g;
+s/^/export /;
+s/=/='/;
+s///g;
+s/$/'/;