cmake: Toolchain abstraction: build-id,gc-sections to toolchain_ld_base

Move --gc-sections flag to toolchain_ld_base()
Move --build-id=none flag to toolchain_ld_base()

No functional change expected.

This is motivated by the wish to abstract Zephyr's usage of toolchains,
permitting non-intrusive porting to other (commercial) toolchains.

Signed-off-by: Mark Ruvald Pedersen <mped@oticon.com>

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 91c369c..cb58f2f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -376,11 +376,6 @@
   endif()
 endif()
 
-zephyr_ld_options(
-  ${LINKERFLAGPREFIX},--gc-sections
-  ${LINKERFLAGPREFIX},--build-id=none
-  )
-
 # Sort the common symbols and each input section by alignment
 # in descending order to minimize padding between these symbols.
 zephyr_ld_option_ifdef(

cmake/linker/ld/target_baremetal.cmake

diff --git a/cmake/linker/ld/target_baremetal.cmake b/cmake/linker/ld/target_baremetal.cmake
index 96d3374..493a556 100644
--- a/cmake/linker/ld/target_baremetal.cmake
+++ b/cmake/linker/ld/target_baremetal.cmake
@@ -4,6 +4,7 @@
 
 macro(toolchain_ld_baremetal)
 
+  # LINKERFLAGPREFIX comes from linker/ld/target.cmake
   zephyr_ld_options(
     -nostdlib
     -static

cmake/linker/ld/target_base.cmake

diff --git a/cmake/linker/ld/target_base.cmake b/cmake/linker/ld/target_base.cmake
index bc0b29e..5a27146 100644
--- a/cmake/linker/ld/target_base.cmake
+++ b/cmake/linker/ld/target_base.cmake
@@ -5,8 +5,11 @@
 macro(toolchain_ld_base)
 
   # TOOLCHAIN_LD_FLAGS comes from compiler/gcc/target.cmake
+  # LINKERFLAGPREFIX comes from linker/ld/target.cmake
   zephyr_ld_options(
     ${TOOLCHAIN_LD_FLAGS}
+    ${LINKERFLAGPREFIX},--gc-sections
+    ${LINKERFLAGPREFIX},--build-id=none
   )
 
 endmacro()