maint/proc: add /sys/proc + migrate to rustc 1.87.0-nightly

etc/aarch64-unknown-none.json

@@ -3,7 +3,7 @@
   "os": "none",
   "abi": "softfloat",
   "llvm-target": "aarch64-unknown-none",
-  "data-layout": "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32",
+  "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32",
   "max-atomic-width": 128,
   "target-pointer-width": "64",
   "features": "+v8a,+strict-align,-neon,-fp-armv8",

etc/x86_64-unknown-none.json

@@ -3,11 +3,12 @@
   "cpu": "x86-64",
   "os": "none",
   "abi": "softfloat",
+  "rustc-abi": "x86-softfloat",
   "llvm-target": "x86_64-unknown-linux-gnu",
   "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
   "max-atomic-width": 64,
   "target-pointer-width": "64",
-  "features": "-avx,-sse,+soft-float",
+  "features": "-avx,-sse,-avx2,+soft-float",
 
   "disable-redzone": true,
   "executables": true,