feat: add Rust userspace support; fix TLS layout for p_align < 16; kill whole process on sibling-thread faults

programs/rust/.cargo/config.toml

@@ -0,0 +1,15 @@
+# Phase 1 Rust support: no_std + alloc on a stock nightly, built with
+# -Zbuild-std against the custom target spec next to this directory.
+# Paths below are relative to programs/rust/ (the parent of .cargo/).
+
+[build]
+target = "x86_64-unknown-montauk.json"
+
+[unstable]
+build-std = ["core", "alloc"]
+json-target-spec = true
+
+[target.x86_64-unknown-montauk]
+# The montauk GCC driver supplies crt1/crti/crtbegin, -lc and libgcc, and
+# links the static non-PIE ET_EXEC layout the kernel ELF loader expects.
+linker = "../../toolchain/local/bin/x86_64-montauk-gcc"