Add NuttX support for AArch64 and ARMv7-A targets

This patch adds tier 3 support for AArch64 and ARMv7-A targets in NuttX,
including:
- AArch64 target: aarch64-unknown-nuttx
- ARMv7-A target: armv7a-nuttx-eabi, armv7a-nuttx-eabihf
- Thumbv7-A target: thumbv7a-nuttx-eabi, thumbv7a-nuttx-eabihf

Signed-off-by: Huang Qi <huangqi3@xiaomi.com>

compiler/rustc_target/src/spec/mod.rs

@@ -1853,6 +1853,8 @@ supported_targets! {
 
     ("armv7a-none-eabi", armv7a_none_eabi),
     ("armv7a-none-eabihf", armv7a_none_eabihf),
+    ("armv7a-nuttx-eabi", armv7a_nuttx_eabi),
+    ("armv7a-nuttx-eabihf", armv7a_nuttx_eabihf),
 
     ("msp430-none-elf", msp430_none_elf),
 
@@ -1896,6 +1898,7 @@ supported_targets! {
 
     ("aarch64-unknown-none", aarch64_unknown_none),
     ("aarch64-unknown-none-softfloat", aarch64_unknown_none_softfloat),
+    ("aarch64-unknown-nuttx", aarch64_unknown_nuttx),
 
     ("x86_64-fortanix-unknown-sgx", x86_64_fortanix_unknown_sgx),
 
@@ -1971,6 +1974,8 @@ supported_targets! {
     ("x86_64-unknown-linux-none", x86_64_unknown_linux_none),
 
     ("thumbv6m-nuttx-eabi", thumbv6m_nuttx_eabi),
+    ("thumbv7a-nuttx-eabi", thumbv7a_nuttx_eabi),
+    ("thumbv7a-nuttx-eabihf", thumbv7a_nuttx_eabihf),
     ("thumbv7m-nuttx-eabi", thumbv7m_nuttx_eabi),
     ("thumbv7em-nuttx-eabi", thumbv7em_nuttx_eabi),
     ("thumbv7em-nuttx-eabihf", thumbv7em_nuttx_eabihf),