diff --git a/tools/build/Makefile b/tools/build/Makefile
--- a/tools/build/Makefile
+++ b/tools/build/Makefile
@@ -88,6 +88,11 @@
 SRCS+=		explicit_bzero.c
 .endif
 
+_WITH_FSPACECTL!= grep -c fspacectl ${HOST_INCLUDE_ROOT}/fcntl.h || true
+.if ${_WITH_FSPACECTL} == 0
+INCS+=		fcntl.h
+SRCS+=		fspacectl.c
+.endif
 
 .if exists(${HOST_INCLUDE_ROOT}/capsicum_helpers.h)
 _WITH_CAPH_ENTER!= grep -c caph_enter ${HOST_INCLUDE_ROOT}/capsicum_helpers.h || true
diff --git a/tools/build/fcntl.h b/tools/build/fcntl.h
new file mode 100644
--- /dev/null
+++ b/tools/build/fcntl.h
@@ -0,0 +1,48 @@
+/*-
+ * Copyright (c) 2016 Jilles Tjoelker <jilles@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _LEGACY_SYS_FCNTL_H_
+#define	_LEGACY_SYS_FCNTL_H_
+
+#include_next <fcntl.h>
+
+struct spacectl_range {
+	off_t	r_offset;
+	off_t	r_len;
+};
+
+#define SPACECTL_DEALLOC	1
+
+#define SPACECTL_F_SUPPORTED	0
+
+__BEGIN_DECLS
+int	fspacectl(int, int, const struct spacectl_range *, int,
+	    struct spacectl_range *);
+__END_DECLS
+
+#endif /* !_LEGACY_SYS_STAT_H_ */
diff --git a/tools/build/fspacectl.c b/tools/build/fspacectl.c
new file mode 100644
--- /dev/null
+++ b/tools/build/fspacectl.c
@@ -0,0 +1,44 @@
+/*-
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software was developed by Ka Ho Ng <khng@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <errno.h>
+#include <fcntl.h>
+
+/*
+ * This is currently a stub implementation of fspacectl(2).
+ */
+int
+fspacectl(int fd, int cmd, const struct spacectl_range *rqsr, int flags,
+    struct spacectl_range *rmsr)
+{
+        errno = ENOSYS;
+        return (-1);
+}
\ No newline at end of file