[ATfE] Do not build aarch64r soft_nofp variants with newlib/llvmlibc (#110)

The aarch64r soft_nofp variants will fail to build using newlib. The
aarch64a soft_nofp variants are already disabled in newlib/llvmlibc
builds due to missing support, so the aarch64r should be similarly
limited to picolibc.

Author: dcandler

arm-software/embedded/arm-multilib/json/multilib.json

@@ -87,32 +87,38 @@
         {
             "variant": "aarch64r_soft_nofp_exn_rtti_unaligned",
             "json": "aarch64r_soft_nofp_exn_rtti_unaligned.json",
-            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft"
+            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "aarch64r_soft_nofp_unaligned",
             "json": "aarch64r_soft_nofp_unaligned.json",
-            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft"
+            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "aarch64r_soft_nofp_exn_rtti",
             "json": "aarch64r_soft_nofp_exn_rtti.json",
-            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft -mno-unaligned-access"
+            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft -mno-unaligned-access",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "aarch64r_soft_nofp",
             "json": "aarch64r_soft_nofp.json",
-            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft -mno-unaligned-access"
+            "flags": "--target=aarch64-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft -mno-unaligned-access",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "aarch64r_be_soft_nofp_exn_rtti",
             "json": "aarch64r_be_soft_nofp_exn_rtti.json",
-            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft"
+            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -mabi=aapcs-soft",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "aarch64r_be_soft_nofp",
             "json": "aarch64r_be_soft_nofp.json",
-            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft"
+            "flags": "--target=aarch64_be-unknown-none-elf -march=armv8-r -march=armvX+nofp -march=armvX+nosimd -fno-exceptions -fno-rtti -mabi=aapcs-soft",
+            "libraries_supported": "picolibc"
         },
         {
             "variant": "armv4t_exn_rtti",