build: Replace `make config` with a `./configure` script

This lets us do more traditional out-of-tree builds like

    $ ../path/to/bfs/configure
    $ make

The .mk files are moved from ./config to ./build, mostly so that
./configure will auto-complete easily.

1 files changed, 12 insertions, 0 deletions

diff --git a/build/has/st-acmtim.c b/build/has/st-acmtim.c
new file mode 100644
index 0000000..d687ab0
--- /dev/null
+++ b/build/has/st-acmtim.c
@@ -0,0 +1,12 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include <sys/stat.h>
+
+int main(void) {
+	struct stat sb = {0};
+	unsigned int a = sb.st_atim.tv_sec;
+	unsigned int c = sb.st_ctim.tv_sec;
+	unsigned int m = sb.st_mtim.tv_sec;
+	return a + c + m;
+}