!944 优化strcspn函数

Merge pull request !944 from fangting/master

musl_src.gni

@@ -2202,6 +2202,7 @@ musl_src_porting_file = [
   "src/env/getenv.c",
   "src/string/stpncpy.c",
   "src/string/strncpy.c",
+  "src/string/strcspn.c",
   "src/thread/pthread_once.c",
   "src/thread/pthread_cancel.c",
   "src/mq/mq_notify.c",

porting/linux/user/src/string/strcspn.c

+// from openbsd, will be rectified later 
+
+#include <string.h>
+
+size_t strcspn(const char *string1, const char *string2)
+{
+	const char *a, *p;
+	char sc, c;
+    
+	for (a = string1;;) {
+		sc = *a++;
+		p = string2;
+		do {
+			if ((c = *p++) == sc)
+				return (a - 1 - string1);
+		} while (c != 0);
+	}
+	/* NOTREACHED */
+}
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