Index: head/share/mk/bsd.lib.mk
===================================================================
--- head/share/mk/bsd.lib.mk
+++ head/share/mk/bsd.lib.mk
@@ -3,6 +3,8 @@
 #
 
 .include <bsd.init.mk>
+.include <bsd.compiler.mk>
+.include <bsd.linker.mk>
 
 .if defined(LIB_CXX) || defined(SHLIB_CXX)
 _LD=	${CXX}
@@ -74,9 +76,13 @@
 LDFLAGS+= -Wl,-znow
 .endif
 .if ${MK_RETPOLINE} != "no"
+.if ${COMPILER_FEATURES:Mretpoline} && ${LINKER_FEATURES:Mretpoline}
 CFLAGS+= -mretpoline
 CXXFLAGS+= -mretpoline
 LDFLAGS+= -Wl,-zretpolineplt
+.else
+.warning Retpoline requested but not supported by compiler or linker
+.endif
 .endif
 
 .if ${MK_DEBUG_FILES} != "no" && empty(DEBUG_FLAGS:M-g) && \
Index: head/share/mk/bsd.prog.mk
===================================================================
--- head/share/mk/bsd.prog.mk
+++ head/share/mk/bsd.prog.mk
@@ -3,6 +3,7 @@
 
 .include <bsd.init.mk>
 .include <bsd.compiler.mk>
+.include <bsd.linker.mk>
 
 .SUFFIXES: .out .o .bc .c .cc .cpp .cxx .C .m .y .l .ll .ln .s .S .asm
 
@@ -44,11 +45,15 @@
 LDFLAGS+= -pie
 .endif
 .if ${MK_RETPOLINE} != "no"
+.if ${COMPILER_FEATURES:Mretpoline} && ${LINKER_FEATURES:Mretpoline}
 CFLAGS+= -mretpoline
 CXXFLAGS+= -mretpoline
 # retpolineplt is broken with static linking (PR 233336)
 .if !defined(NO_SHARED) || ${NO_SHARED:tl} == "no"
 LDFLAGS+= -Wl,-zretpolineplt
+.endif
+.else
+.warning Retpoline requested but not supported by compiler or linker
 .endif
 .endif