regex: avoid a namespace collision with C23 <float.h>.

Bug: http://b/384985989
Test: presubmit
Change-Id: I8173cb185fc329b356c3741be6f13f1c5367dc88

diff --git a/lib/Support/regcomp.c b/lib/Support/regcomp.c
index ebde64f..ac7bb8c 100644
--- a/lib/Support/regcomp.c
+++ b/lib/Support/regcomp.c
@@ -150,6 +150,7 @@
 #else
 #define	DUPMAX	255
 #endif
+#undef INFINITY // Android-added: avoid collision with C23 <float.h> INFINITY (via <limits.h>)
 #define	INFINITY	(DUPMAX + 1)
 
 #ifndef NDEBUG