Split out tests into its own file

Also adjust the build system to do some more (cleaning, building,
testing, running).

sv.c

@@ -0,0 +1,27 @@
+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the Unlicense
+ * for details.
+
+ * You may distribute and modify this code under the terms of the
+ * Unlicense, which you should have received a copy of along with this
+ * program.  If not, please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-21
+ * Description: String views
+ */
+
+#include <malloc.h>
+#include <string.h>
+
+#include "./alisp.h"
+
+sv_t sv_copy(sv_t old)
+{
+  char *newstr = calloc(1, (old.size + 1) * sizeof(*newstr));
+  memcpy(newstr, old.data, old.size);
+  newstr[old.size] = '\0';
+  return SV(newstr, old.size);
+}