kconfig: cmake: CMake linker script generator symbol added

A "Linker script" choice group has been added to the linker options
menu.

The existing HAVE_CUSTOM_LINKER_SCRIPT config has been relocated inside
the linker script menu.

Two new entries has been created:
- LD template, for using the old ld template files together with the C
  pre-processor to create the final linker script.
- CMake linker generator, used for ARMClang / armlink toolchain.
  The CMake linker generator is also supported for LD linker scripts
  for the ARM architecture.

In CMake, the file cmake/linker/ld/target.cmake has been updated to
support the CMake LD linker generator.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

Kconfig.zephyr

@@ -132,8 +132,36 @@ config ROM_START_OFFSET
 	  alignment requirements on most ARM targets, although some targets
 	  may require smaller or larger values.
 
+config LD_LINKER_SCRIPT_SUPPORTED
+	bool
+	default y
+
+choice LINKER_SCRIPT
+	prompt "Linker script"
+	default LD_LINKER_TEMPLATE if LD_LINKER_SCRIPT_SUPPORTED
+
+config LD_LINKER_TEMPLATE
+	bool "LD template"
+	depends on LD_LINKER_SCRIPT_SUPPORTED
+	help
+	  Select this option to use the LD linker script templates.
+	  The templates are pre-processed by the C pre-processor to create the
+	  final LD linker script.
+
+config CMAKE_LINKER_GENERATOR
+	bool "CMake generator"
+	depends on ARM
+	help
+	  Select this option to use the Zephyr CMake linker script generator.
+	  The linker configuration is written in CMake and the final linker
+	  script will be generated by the toolchain specific linker generator.
+	  For LD based linkers, this will be the ld generator, for ARMClang /
+	  armlink based linkers it will be the scatter generator.
+
+endchoice
+
 config HAVE_CUSTOM_LINKER_SCRIPT
-	bool "Custom linker scripts provided"
+	bool "Custom linker script provided"
 	help
 	  Set this option if you have a custom linker script which needed to
 	  be define in CUSTOM_LINKER_SCRIPT.