grep/pcre2: use compile-time PCREv2 version test

Replace a use of pcre2_config(PCRE2_CONFIG_VERSION, ...) which I added
in 95ca1f987e (grep/pcre2: better support invalid UTF-8 haystacks,
2021-01-24) with the same test done at compile-time.

It might be cuter to do this at runtime since we don't have to do the
"major >= 11 || (major >= 10 && ...)" test. But in the next commit
we'll add another version comparison that absolutely needs to be done
at compile-time, so we're better of being consistent across the board.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

grep.c

@@ -400,21 +400,11 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
 	    !(!opt->ignore_case && (p->fixed || p->is_fixed)))
 		options |= (PCRE2_UTF | PCRE2_MATCH_INVALID_UTF);
 
+#ifdef GIT_PCRE2_VERSION_10_36_OR_HIGHER
 	/* Work around https://bugs.exim.org/show_bug.cgi?id=2642 fixed in 10.36 */
-	if (PCRE2_MATCH_INVALID_UTF && options & (PCRE2_UTF | PCRE2_CASELESS)) {
-		struct strbuf buf;
-		int len;
-		int err;
-
-		if ((len = pcre2_config(PCRE2_CONFIG_VERSION, NULL)) < 0)
-			BUG("pcre2_config(..., NULL) failed: %d", len);
-		strbuf_init(&buf, len + 1);
-		if ((err = pcre2_config(PCRE2_CONFIG_VERSION, buf.buf)) < 0)
-			BUG("pcre2_config(..., buf.buf) failed: %d", err);
-		if (versioncmp(buf.buf, "10.36") < 0)
-			options |= PCRE2_NO_START_OPTIMIZE;
-		strbuf_release(&buf);
-	}
+	if (PCRE2_MATCH_INVALID_UTF && options & (PCRE2_UTF | PCRE2_CASELESS))
+		options |= PCRE2_NO_START_OPTIMIZE;
+#endif
 
 	p->pcre2_pattern = pcre2_compile((PCRE2_SPTR)p->pattern,
 					 p->patternlen, options, &error, &erroffset,

grep.h

@@ -4,6 +4,9 @@
 #ifdef USE_LIBPCRE2
 #define PCRE2_CODE_UNIT_WIDTH 8
 #include <pcre2.h>
+#if (PCRE2_MAJOR >= 10 && PCRE2_MINOR >= 36) || PCRE2_MAJOR >= 11
+#define GIT_PCRE2_VERSION_10_36_OR_HIGHER
+#endif
 #else
 typedef int pcre2_code;
 typedef int pcre2_match_data;