Red Bear OS — microkernel OS in Rust, based on Redox

Derivative of Redox OS (https://www.redox-os.org) adding:
- AMD GPU driver (amdgpu) via LinuxKPI compat layer
- ext4 filesystem support (ext4d scheme daemon)
- ACPI fixes for AMD bare metal (x2APIC, DMAR, IVRS, MCFG)
- Custom branding (hostname, os-release, boot identity)

Build system is full upstream Redox with RBOS overlay in local/.
Patches for kernel, base, and relibc are symlinked from local/patches/
and protected from make clean/distclean. Custom recipes live in
local/recipes/ with symlinks into the recipes/ search path.

Build:  make all CONFIG_NAME=redbear-full
Sync:   ./local/scripts/sync-upstream.sh

local/patches/base/P0-acpid-dmar-fix.patch

@@ -0,0 +1,19 @@
+diff --git a/drivers/acpid/src/acpi/dmar/mod.rs b/drivers/acpid/src/acpi/dmar/mod.rs
+--- a/drivers/acpid/src/acpi/dmar/mod.rs
++++ b/drivers/acpid/src/acpi/dmar/mod.rs
+@@ -475,8 +475,12 @@ impl<'sdt> Iterator for DmarRawIter<'sdt> {
+             .expect("expected a 2-byte slice to be convertible to [u8; 2]");
+ 
+-        let ty = u16::from_ne_bytes(type_bytes);
+-        let len = u16::from_ne_bytes(len_bytes);
++        let len = u16::from_ne_bytes(len_bytes) as usize;
++
++        if len < 4 {
++            return None;
++        }
++
++        let ty = u16::from_ne_bytes(type_bytes);
+ 
+-        let len = usize::try_from(len).expect("expected u16 to fit within usize");
+ 
+         if len > remainder.len() {