Fixing test builds for devices with softdevices.

Previously, .hex files were not copied when building source as a library.
This prevents builds that pre compile source as a library and then
includes the build directory as the only source (because there is no
softdevice present). This PR copies hex files when compiling source
as a library.

tools/build_api.py

@@ -311,6 +311,9 @@ def build_library(src_paths, build_path, target, toolchain_name,
             if resource.linker_script:
                 toolchain.copy_files(resource.linker_script, build_path, rel_path=resource.base_path)
                 
+            if resource.hex_files:
+                toolchain.copy_files(resource.hex_files, build_path, rel_path=resource.base_path)
+
             # Extend resources collection
             if not resources:
                 resources = resource
@@ -494,6 +497,7 @@ def build_lib(lib_id, target, toolchain_name, options=None, verbose=False, clean
         # Copy Headers
         for resource in resources:
             toolchain.copy_files(resource.headers, build_path, rel_path=resource.base_path)
+            
         dependencies_include_dir.extend(toolchain.scan_resources(build_path).inc_dirs)
 
         # Compile Sources