ckermit: Define return type for main

Newer compilers e.g. clang19+ will treat implicit function prototypes
as errors, therefore define main() with a valid return type

Fixes
ckwart.c:531:1: error: return type defaults to ‘int’ [-Wimplicit-int]
  531 | main(argc,argv) int argc; char **argv; {
      | ^~~~

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-support/ckermit/ckermit_302.bb

@@ -45,7 +45,7 @@ do_compile () {
         -DNORESEND -DNOAUTODL -DNOSTREAMING -DNOHINTS -DNOCKXYZ -DNOLEARN \
         -DNOMKDIR -DNOPERMS -DNOCKTIMERS -DNOCKREGEX -DNOREALPATH \
         -DCK_SMALL -DNOLOGDIAL -DNORENAME -DNOWHATAMI \
-        -DNOARROWKEYS"
+        -DNOARROWKEYS -DMAINTYPE=int"
 }
 
 do_install () {