Improve error parsing for GCC -fanalyzer output

* compile.el (compilation-error-regexp-alist-alist): Adjust gnu rule
* compile-tests.el (compile-tests--test-regexps-data): Add testcase

lisp/progmodes/compile.el

@@ -351,7 +351,10 @@ of[ \t]+\"?\\([a-zA-Z]?:?[^\":\n]+\\)\"?:" 3 2 nil (1))
              ;; from Ruby, but it is unclear whether it is actually
              ;; used since the gcc-include rule above seems to cover
              ;; it.
-             (regexp "[ \t]+\\(?:in \\|from\\)")))
+             (regexp "[ \t]+\\(?:in \\|from\\)")
+             ;; Skip indentation generated by tools like GCC's
+             ;; -fanalyzer.
+             (: (+ space) "|")))
 
        ;; File name group.
        (group-n 1

test/lisp/progmodes/compile-tests.el

@@ -230,6 +230,7 @@
     (gnu "foo.c:8:23:information: message" 1 23 8 "foo.c")
     (gnu "foo.c:8.23-45: Informational: message" 1 (23 . 45) (8 . nil) "foo.c")
     (gnu "foo.c:8-23: message" 1 nil (8 . 23) "foo.c")
+    (gnu "   |foo.c:8: message" 1 nil 8 "foo.c")
     ;; The next one is not in the GNU standards AFAICS.
     ;; Here we seem to interpret it as LINE1-LINE2.COL2.
     (gnu "foo.c:8-45.3: message" 1 (nil . 3) (8 . 45) "foo.c")