rust: Initial config option

Add the `CONFIG_RUST` Kconfig.  This can be set to indicate that an
application wishes to use Rust support.

Adds `CONFIG_RUST_SUPPORTED` to indicate what platforms Rust is known to
work on.  This is set to the targets that are supported by subsequent
commits.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

lib/Kconfig

@@ -21,6 +21,8 @@ source "lib/posix/Kconfig"
 
 source "lib/open-amp/Kconfig"
 
+source "lib/rust/Kconfig"
+
 source "lib/smf/Kconfig"
 
 source "lib/acpi/Kconfig"

lib/rust/Kconfig

@@ -0,0 +1,22 @@
+# Rust configuration options
+#
+# Copyright (c) 2024 Linaro LTD
+# SPDX-License-Identifier: Apache-2.0
+
+menu "Rust Language Support"
+
+config RUST_SUPPORTED
+	bool
+	default y if (CPU_CORTEX_M || \
+		(RISCV && !RISCV_ISA_RV32E && !RISCV_ISA_RV128I))
+	help
+	  Selected for platforms that have support for Rust.
+
+config RUST
+	bool "Rust support for the application"
+	depends on RUST_SUPPORTED
+	select EXPERIMENTAL
+	help
+	  This option enables the use of applications written in Rust.
+
+endmenu