Add target_env = "macabi" and target_env = "sim"

Replaces `target_abi` variants. The old variants are still available,
but may be deprecated in the future.

Author: madsmtm

src/conditional-compilation.md

@@ -196,17 +196,19 @@ Example values:
 * `"msvc"`
 * `"musl"`
 * `"sgx"`
+* `"sim"`
+* `"macabi"`
 
 r[cfg.target_abi]
 ### `target_abi`
 
 r[cfg.target_abi.general]
-Key-value option set to further disambiguate the `target_env` with information
-about the target ABI.
+Key-value option set to further disambiguate the `target_env` or `target_arch`
+with information about the target ABI.
 
 r[cfg.target_abi.disambiguation]
 For historical reasons, this value is only defined as not the empty-string when actually
- needed for disambiguation. Thus, for example, on many GNU platforms, this value will be
+needed for disambiguation. Thus, for example, on many GNU platforms, this value will be
 empty.
 
 r[cfg.target_abi.values]
@@ -216,8 +218,6 @@ Example values:
 * `"llvm"`
 * `"eabihf"`
 * `"abi64"`
-* `"sim"`
-* `"macabi"`
 
 r[cfg.target_endian]
 ### `target_endian`