Add a development eBPF container build

See `docs/ebpf.md` for how to use. This is built by CI or you can build
manually if you customise the kernel.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

alpine/base/ebpf/error.h

@@ -0,0 +1,29 @@
+# include <stdio.h>
+# include <stdarg.h>
+# include <stdlib.h>
+# include <string.h>
+static void error_at_line(int status, int errnum, const char *filename,
+                          unsigned int linenum, const char *format, ...)
+{
+	va_list ap;
+
+	fflush(stdout);
+
+	if (filename != NULL)
+		fprintf(stderr, "%s:%u: ", filename, linenum);
+
+	va_start(ap, format);
+	vfprintf(stderr, format, ap);
+	va_end(ap);
+
+	if (errnum != 0)
+		fprintf(stderr, ": %s", strerror(errnum));
+
+	fprintf(stderr, "\n");
+
+	if (status != 0)
+		exit(status);
+}
+
+#define error(status, errnum, format...) \
+	error_at_line(status, errnum, NULL, 0, format)