Build: Fix GNU "specs" command line argument prefix

GNU 12.2.Rel1 only parse this argument with one "-".
Every ARM GNU manuals contains "-specs" instead of "--specs".

Signed-off-by: Dávid Házi <david.hazi@arm.com>
Change-Id: I206930d65ac0f7d47fb693e9ec8dc8cbc884dffc
diff --git a/toolchain_GNUARM.cmake b/toolchain_GNUARM.cmake
index d044ed4..9bfb7b4 100644
--- a/toolchain_GNUARM.cmake
+++ b/toolchain_GNUARM.cmake
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2020-2022, Arm Limited. All rights reserved.
+# Copyright (c) 2020-2023, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -39,7 +39,7 @@
     endif()
 
     add_compile_options(
-        --specs=nano.specs
+        -specs=nano.specs
         -Wall
         -Wno-format
         -Wno-return-type
@@ -69,7 +69,7 @@
 
     add_link_options(
         --entry=Reset_Handler
-        --specs=nano.specs
+        -specs=nano.specs
         LINKER:-check-sections
         LINKER:-fatal-warnings
         LINKER:--gc-sections