buildhistory-collect-srcrevs: Adapt to the new variable override syntax

(From OE-Core rev: bcce0e7cef5768d5cfe58c356f6196af8ce03537)

Signed-off-by: Peter Kjellerstedt <peter.kjellerstedt@axis.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/buildhistory-collect-srcrevs

@@ -53,7 +53,7 @@ def main():
         sys.exit(1)
 
     if options.forcevariable:
-        forcevariable = '_forcevariable'
+        forcevariable = ':forcevariable'
     else:
         forcevariable = ''
 
@@ -99,7 +99,7 @@ def main():
             print('# %s' % curdir)
             for pn, name, srcrev in srcrevs:
                 if name:
-                    print('SRCREV_%s_pn-%s%s = "%s"' % (name, pn, forcevariable, srcrev))
+                    print('SRCREV_%s:pn-%s%s = "%s"' % (name, pn, forcevariable, srcrev))
                 else:
                     print('SRCREV:pn-%s%s = "%s"' % (pn, forcevariable, srcrev))