patch 9.0.0088: pattern for detecting bitbake files is not sufficient

Problem:    Pattern for detecting bitbake files is not sufficient.
Solution:   Adjust the pattern. (Gregory Anders, closes #10743)
diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 708a42a..e48575c 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -519,7 +519,7 @@
     # headers so assume POV-Ray
     elseif lines =~ '^\s*\%({\|(\*\)' || lines =~? ft_pascal_keywords
       setf pascal
-    elseif lines =~# '\<\%(require\|inherit\)\>' || lines =~# '\w\+ = '
+    elseif lines =~# '\<\%(require\|inherit\)\>' || lines =~# '[A-Z][A-Za-z0-9_:${}]*\s\+\%(??\|[?:+]\)\?= '
       setf bitbake
     else
       FTasmsyntax()