diff --git a/tools/build/Makefile b/tools/build/Makefile
--- a/tools/build/Makefile
+++ b/tools/build/Makefile
@@ -196,9 +196,15 @@
 SRCS+=	rpmatch.c
 
 .if ${.MAKE.OS} == "Linux"
-# On Linux, glibc does not provide strlcpy,strlcat or strmode.
+# On Linux, glibc does not provide strmode. It only provides strlcpy
+# and strlcat from glibc 2.38.
 .PATH: ${LIBC_SRCTOP}/string
-SRCS+=	strlcpy.c strlcat.c strmode.c
+SRCS+=	strmode.c
+# Assume if strlcpy exists so does strlcat
+_WITH_EXPLICIT_STRLCPY!= cat ${HOST_INCLUDE_ROOT}/strings.h ${HOST_INCLUDE_ROOT}/string.h | grep -c strlcpy || true
+.if ${_WITH_EXPLICIT_STRLCPY} == 0
+SRCS+=	strlcpy.c strlcat.c
+.endif
 # On Linux, glibc provides ffs* but not fls*
 SRCS+=	fls.c flsl.c flsll.c
 # Compile the fgetln/fgetwln/closefrom fallback code from libbsd:
diff --git a/tools/build/cross-build/include/linux/string.h b/tools/build/cross-build/include/linux/string.h
--- a/tools/build/cross-build/include/linux/string.h
+++ b/tools/build/cross-build/include/linux/string.h
@@ -47,8 +47,11 @@
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
+#if !defined(__GLIBC__) || \
+    (defined(__GLIBC__) && (!__GLIBC_PREREQ(2, 38) || !defined(_GNU_SOURCE)))
 size_t strlcpy(char *dst, const char *src, size_t siz);
 size_t strlcat(char *dst, const char *src, size_t siz);
+#endif
 char *strnstr(const char *str, const char *find, size_t str_len);
 void strmode(mode_t mode, char *str);