Auto merge of #81346 - hug-dev:nonsecure-call-abi, r=jonas-schievink

Add a new ABI to support cmse_nonsecure_call

This adds support for the `cmse_nonsecure_call` feature to be able to perform non-secure function call.

See the discussion on Zulip [here](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Support.20for.20callsite.20attributes/near/223054928).

This is a followup to #75810 which added `cmse_nonsecure_entry`. As for that PR, I assume that the changes are small enough to not have to go through a RFC but I don't mind doing one if needed 😃
I did not yet create a tracking issue, but if most of it is fine, I can create one and update the various files accordingly (they refer to the other tracking issue now).

On the Zulip chat, I believe `@jonas-schievink` volunteered to be a reviewer 💯

compiler/rustc_target/src/abi/call/mod.rs

@@ -551,6 +551,7 @@ pub enum Conv {
 
     // Target-specific calling conventions.
     ArmAapcs,
+    CCmseNonSecureCall,
 
     Msp430Intr,
 

compiler/rustc_target/src/spec/abi.rs

@@ -36,6 +36,7 @@ pub enum Abi {
     EfiApi,
     AvrInterrupt,
     AvrNonBlockingInterrupt,
+    CCmseNonSecureCall,
 
     // Multiplatform / generic ABIs
     System,
@@ -81,6 +82,7 @@ const AbiDatas: &[AbiData] = &[
         name: "avr-non-blocking-interrupt",
         generic: false,
     },
+    AbiData { abi: Abi::CCmseNonSecureCall, name: "C-cmse-nonsecure-call", generic: false },
     // Cross-platform ABIs
     AbiData { abi: Abi::System, name: "system", generic: true },
     AbiData { abi: Abi::RustIntrinsic, name: "rust-intrinsic", generic: true },