bsd.linker.mk: Retire support for binutils 2.17.50

GNU binutils 2.17.50 is the last GPLv2 version, and we retained support
in FreeBSD while it was part of the in-tree toolchain.  The last parts
of binutils 2.17.50 were removed in commit 74e8d41e0a ("Retire
BINUTILS and BINUTILS_BOOTSTRAP options") and there is no longer a need
for the build infrastructure.

We retain build-id and ifunc in LINKER_FEATURES unconditionally for now,
as they may be tested by 3rd-party Makefiles.  We can however stop
testing for them in the tree.

Reviewed by:	imp
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55674

share/mk/bsd.linker.mk

@@ -104,11 +104,9 @@ ${X_}LINKER_VERSION!=	echo "${_v:M[1-9]*.[0-9]*}" | \
 .undef _ld_version
 .undef _v
 ${X_}LINKER_FEATURES=
-.if ${${X_}LINKER_TYPE} != "bfd" || ${${X_}LINKER_VERSION} > 21750
 ${X_}LINKER_FEATURES+=	build-id
 ${X_}LINKER_FEATURES+=	ifunc
-.endif
-.if ${${X_}LINKER_TYPE} == "bfd" && ${${X_}LINKER_VERSION} > 21750
+.if ${${X_}LINKER_TYPE} == "bfd"
 ${X_}LINKER_FEATURES+=	riscv-relaxations
 .endif
 .if ${${X_}LINKER_TYPE} == "lld" && ${${X_}LINKER_VERSION} >= 60000