Make it explicit that bootstrap is statically linked

Even if we start using dynamic linking for the rest of initfs, bootstrap
has to be statically linked as it is responsible for loading the first
instance of the dynamic linker.

recipes/core/base-initfs/recipe.toml

@@ -106,7 +106,7 @@ cp "${COOKBOOK_BUILD}/initfs/bin/zerod" "${COOKBOOK_BUILD}/initfs/bin/nulld"
 cp "${COOKBOOK_SYSROOT}/usr/bin/redoxfs" "${COOKBOOK_BUILD}/initfs/bin"
 
 ARCH="$(echo "${GNU_TARGET}" | cut -d - -f1)"
-cargo \
+RUSTFLAGS="$RUSTFLAGS -Ctarget-feature=+crt-static" cargo \
     -Zbuild-std=core,alloc,compiler_builtins \
     -Zbuild-std-features=compiler-builtins-mem build \
     --target "${TARGET}" \