libc: Add strchrnul()

Another GNU extension, it's ok.

libs/libc/include/string.h

@@ -49,6 +49,10 @@ extern "C"
     /* Returns a pointer to the last occurrence of the character c in str, or NULL if it is not found. */
     char* strrchr(const char* str, int c);
 
+    /* Returns a pointer to the first occurrence of the character c in str, or a pointer to the terminating null byte of
+     * str if it is not found. */
+    char* strchrnul(const char* str, int c);
+
     /* Concatenates at most max bytes of the string src into dest. */
     char* strncat(char* dest, const char* src, size_t max);
 

libs/libc/src/string.cpp

@@ -208,6 +208,12 @@ extern "C"
         return NULL;
     }
 
+    char* strchrnul(const char* str, int c)
+    {
+        while (*str && *str != (char)c) str++;
+        return const_cast<char*>(str);
+    }
+
     char* strrchr(const char* str, int c)
     {
         const char* s = str + strlen(str);