gbuild-to-ide: fix VimIntegrationGenerator

Regression from commit 92c2c5f62d
(gbuild-to-ide: moduleDict targets -> all paths replaced with relative,
2017-01-24), <https://clang.llvm.org/docs/JSONCompilationDatabase.html>
says about the "directory" key of one entry:

"All paths specified in the command or file fields must be either
absolute or relative to this directory."

So making the includes relative to the toplevel directory won't fly,
make them absolute.

Change-Id: I3f33c7a21880c1b245580b22996079ba08e3d806
Reviewed-on: https://gerrit.libreoffice.org/33694
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

bin/gbuild-to-ide

@@ -1118,7 +1118,7 @@ class VimIntegrationGenerator(IdeIntegrationGenerator):
 
         for include in lib['include']:
             command += ' -I'
-            command += include
+            command += os.path.abspath(include)
         for isystem in lib['include_sys']:
             command += ' -isystem '
             command += isystem