PrmPkg: Build Prm Samples with GCC for AARCH64

- Add the --prm flag to the GENFW_FLAGS
- Add the --no-gc-section to the linker flags so that apparently
unreferenced symbols are not prematurely removed from the .dll which
is used to generate the Prm module .efi.
- Force the linker to maintain the PrmModuleExportDescriptor symbol.
- Force the linker to maintain the PRM handler funtion's symbol.

Signed-off-by: Jose Marinho <jose.marinho@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>

PrmPkg/Samples/PrmSampleAcpiParameterBufferModule/PrmSampleAcpiParameterBufferModule.inf

@@ -7,6 +7,7 @@
 #  code at OS runtime.
 #
 #  Copyright (c) Microsoft Corporation
+#  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -39,3 +40,6 @@
 [BuildOptions.common]
   MSFT:*_*_*_DLINK_FLAGS  = /DLL /SUBSYSTEM:CONSOLE /VERSION:1.0
   MSFT:*_*_*_GENFW_FLAGS = --keepoptionalheader
+
+  GCC:*_*_AARCH64_GENFW_FLAGS = --prm
+  GCC:*_*_AARCH64_DLINK_FLAGS = -Wl,--no-gc-sections -Wl,--require-defined=PrmModuleExportDescriptor -Wl,--require-defined=CheckParamBufferPrmHandler

PrmPkg/Samples/PrmSampleContextBufferModule/PrmSampleContextBufferModule.inf

@@ -7,6 +7,7 @@
 #
 #  Copyright (c) 2020, Intel Corporation. All rights reserved.<BR>
 #  Copyright (c) Microsoft Corporation
+#  Copyright (c) 2022, Arm Limited. All rights reserved.<BR>
 #
 #  SPDX-License-Identifier: BSD-2-Clause-Patent
 #
@@ -42,3 +43,6 @@
 [BuildOptions.common]
   MSFT:*_*_*_DLINK_FLAGS  = /DLL /SUBSYSTEM:CONSOLE /VERSION:1.0
   MSFT:*_*_*_GENFW_FLAGS = --keepoptionalheader
+
+  GCC:*_*_AARCH64_GENFW_FLAGS = --keepoptionalheader --prm
+  GCC:*_*_AARCH64_DLINK_FLAGS = -Wl,--no-gc-sections -Wl,--require-defined=PrmModuleExportDescriptor -Wl,--require-defined=CheckStaticDataBufferPrmHandler