add: strcmp

src/string/strcmp.c

@@ -0,0 +1,10 @@
+#include <stddef.h>
+
+int strcmp(const char *s1, const char *s2)
+{
+	size_t i = 0;
+
+	while (s1[i] == s2[i] && s1[i] != '\0')
+		i++;
+	return s1[i] - s2[i];
+}