Fixes in the AArch64 nofp variants regarding RTTI and exceptions (#594)

This patch fixes a few issues in the AArch64 nofp variants:

- AArch64 nofp variants without exceptions and RTTI must have higher
priority
    
    The presence of `-fno-exceptions` and `-fno-rtti` in the driver
    invocation causes matching with two variants: the one with
    RTTI/Exceptions and the one without.
    
In the multilib system, the last match is the one that wins, therefore
    in the JSON file we must list the variant without RTTI/Exceptions
    *after* the one with.

- Enable exceptions and RTTI in the build of aarch64 nofp variants
supposed to have them

arm-multilib/json/multilib.json

@@ -30,31 +30,30 @@
             "json": "aarch64a_strictalign.json",
             "flags": "--target=aarch64-unknown-none-elf -mno-unaligned-access -fno-exceptions -fno-rtti"
         },
-        {
-            "variant": "aarch64a_soft_nofp",
-            "json": "aarch64a_soft_nofp.json",
-            "flags": "--target=aarch64-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft -fno-exceptions -fno-rtti",
-            "libraries_supported": "picolibc,newlib"
-        },
-        {
-            "variant": "aarch64a_be_soft_nofp",
-            "json": "aarch64a_be_soft_nofp.json",
-            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft -fno-exceptions -fno-rtti",
-            "libraries_supported": "picolibc,newlib"
-        },
         {
             "variant": "aarch64a_soft_nofp_exn_rtti",
             "json": "aarch64a_soft_nofp_exn_rtti.json",
             "flags": "--target=aarch64-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft",
             "libraries_supported": "picolibc,newlib"
         },
+        {
+            "variant": "aarch64a_soft_nofp",
+            "json": "aarch64a_soft_nofp.json",
+            "flags": "--target=aarch64-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft -fno-exceptions -fno-rtti",
+            "libraries_supported": "picolibc,newlib"
+        },
         {
             "variant": "aarch64a_be_soft_nofp_exn_rtti",
             "json": "aarch64a_be_soft_nofp_exn_rtti.json",
             "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft",
             "libraries_supported": "picolibc,newlib"
         },
-
+        {
+            "variant": "aarch64a_be_soft_nofp",
+            "json": "aarch64a_be_soft_nofp.json",
+            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-a+nofp+nosimd -mabi=aapcs-soft -fno-exceptions -fno-rtti",
+            "libraries_supported": "picolibc,newlib"
+        },
         {
             "variant": "armv4t_exn_rtti",
             "json": "armv4t_exn_rtti.json",

arm-multilib/json/variants/aarch64a_be_soft_nofp_exn_rtti.json

@@ -4,8 +4,8 @@
             "TARGET_ARCH": "aarch64a",
             "VARIANT": "aarch64a_be_soft_nofp_exn_rtti",
             "COMPILE_FLAGS": "-march=armv8-a+nofp+nosimd -mbig-endian -mabi=aapcs-soft -mno-unaligned-access",
-            "ENABLE_EXCEPTIONS": "OFF",
-            "ENABLE_RTTI": "OFF",
+            "ENABLE_EXCEPTIONS": "ON",
+            "ENABLE_RTTI": "ON",
             "TEST_EXECUTOR": "fvp",
             "FVP_MODEL": "aem-a",
             "FVP_CONFIG": "v8a-aarch64 big-endian",

arm-multilib/json/variants/aarch64a_soft_nofp_exn_rtti.json

@@ -4,8 +4,8 @@
             "TARGET_ARCH": "aarch64a",
             "VARIANT": "aarch64a_soft_nofp_exn_rtti",
             "COMPILE_FLAGS": "-march=armv8-a+nofp+nosimd -mabi=aapcs-soft -mno-unaligned-access",
-            "ENABLE_EXCEPTIONS": "OFF",
-            "ENABLE_RTTI": "OFF",
+            "ENABLE_EXCEPTIONS": "ON",
+            "ENABLE_RTTI": "ON",
             "TEST_EXECUTOR": "qemu",
             "QEMU_MACHINE": "virt",
             "QEMU_CPU": "cortex-a57",