fix build failure after commit 2a8d00634ddf if strtod isn't available.
diff --git a/src/stdlib/SDL_string.c b/src/stdlib/SDL_string.c
index d5ce001..7e8c3a7 100644
--- a/src/stdlib/SDL_string.c
+++ b/src/stdlib/SDL_string.c
@@ -53,7 +53,7 @@ static unsigned UTF8_TrailingBytes(unsigned char c)
return 0;
}
-#if !defined(HAVE_VSSCANF) || !defined(HAVE_STRTOL)
+#if !defined(HAVE_VSSCANF) || !defined(HAVE_STRTOL) || !defined(HAVE_STRTOD)
static size_t
SDL_ScanLong(const char *text, int count, int radix, long *valuep)
{