build: Add option to customize the LINKFLAGS

spec/build/bsps/bspopts.yml

@@ -17,6 +17,8 @@ links:
   uid: optfatalverb
 - role: build-dependency
   uid: optincludes
+- role: build-dependency
+  uid: optlinkflags
 - role: build-dependency
   uid: optldflags
 - role: build-dependency

spec/build/bsps/optldflags.yml

@@ -11,7 +11,7 @@ default:
 - -Wl,--gc-sections
 default-by-variant: []
 description: |
-  Flags passed to the linker (GNU ld)
+  Flags passed to the linker at the end of the link command.
 enabled-by: true
 links: []
 name: LDFLAGS

spec/build/bsps/optlinkflags.yml

@@ -0,0 +1,16 @@
+SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
+actions:
+- get-string: null
+- split: null
+- env-append: null
+build-type: option
+copyrights:
+- Copyright (C) 2021 embedded brains GmbH (http://www.embedded-brains.de)
+default: []
+default-by-variant: []
+description: |
+  Flags passed to the linker.
+enabled-by: true
+links: []
+name: LINKFLAGS
+type: build