BaseTools/tools_def ARM: emit PIC veneers

The ARM linker may emit veneers, i.e., trampolines, when ordinary
direct relative branches cannot be used, e.g., for Thumb interworking
or branch targets that are out of range.

Usually, such veneers carry an absolute reference to the branch
target, which is problematic for us, since these absolute references
are not covered by annotations that are visible to GenFw in the
PE/COFF conversion, and so these absolute references are not fixed
up by the PE/COFF loader at runtime.

So switch to all ARM GNU ld toolchains to position independent veneers.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

BaseTools/Conf/tools_def.template

@@ -4150,7 +4150,7 @@ DEFINE GCC_DLINK_FLAGS_COMMON      = -nostdlib --pie
 DEFINE GCC_DLINK2_FLAGS_COMMON     = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds
 DEFINE GCC_IA32_X64_DLINK_COMMON   = DEF(GCC_DLINK_FLAGS_COMMON) --gc-sections
 DEFINE GCC_ARM_AARCH64_DLINK_COMMON= -Wl,--emit-relocs -nostdlib -Wl,--gc-sections -u $(IMAGE_ENTRY_POINT) -Wl,-e,$(IMAGE_ENTRY_POINT),-Map,$(DEST_DIR_DEBUG)/$(BASE_NAME).map
-DEFINE GCC_ARM_DLINK_FLAGS         = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20
+DEFINE GCC_ARM_DLINK_FLAGS         = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20 -Wl,--pic-veneer
 DEFINE GCC_AARCH64_DLINK_FLAGS     = DEF(GCC_ARM_AARCH64_DLINK_COMMON) -z common-page-size=0x20
 DEFINE GCC_ARM_AARCH64_ASLDLINK_FLAGS = -Wl,--defsym=PECOFF_HEADER_SIZE=0 DEF(GCC_DLINK2_FLAGS_COMMON) -z common-page-size=0x20
 DEFINE GCC_IA32_X64_ASLDLINK_FLAGS = DEF(GCC_IA32_X64_DLINK_COMMON) --entry _ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT)