Platform: Fix relative include paths of linker

Instead of using hard-coded relative include paths in the linker
command files, this change sets the include search path
in the command line.

Change-Id: I6d117a5bbf624f7c252f12103dee2afd338f2983
Signed-off-by: Gabor Kertesz <gabor.kertesz@arm.com>
diff --git a/platform/ext/musca_a.cmake b/platform/ext/musca_a.cmake
index 89edff7..0110b53 100755
--- a/platform/ext/musca_a.cmake
+++ b/platform/ext/musca_a.cmake
@@ -13,10 +13,11 @@
 set(PLATFORM_DIR ${CMAKE_CURRENT_LIST_DIR})
 
 #Specify the location of platform specific build dependencies.
-set (BL2_SCATTER_FILE_NAME "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_bl2.sct")
-set (S_SCATTER_FILE_NAME   "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_s.sct")
-set (NS_SCATTER_FILE_NAME  "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_ns.sct")
-set (FLASH_LAYOUT          "${PLATFORM_DIR}/target/musca_a/partition/flash_layout.h")
+set (BL2_SCATTER_FILE_NAME  "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_bl2.sct")
+set (S_SCATTER_FILE_NAME    "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_s.sct")
+set (NS_SCATTER_FILE_NAME   "${PLATFORM_DIR}/target/musca_a/Device/Source/armclang/musca_ns.sct")
+set (FLASH_LAYOUT           "${PLATFORM_DIR}/target/musca_a/partition/flash_layout.h")
+set (PLATFORM_LINK_INCLUDES "${PLATFORM_DIR}/target/musca_a/partition")
 set (SIGN_BIN_SIZE         0x30000)
 if (DEFINED CMSIS_5_DIR)
   # not all project defines CMSIS_5_DIR, only the ones that use it.