Use -Zbuild-std=core in CI; update SECURITY

CI: Add -Zbuild-std=core to the cargo +esp build step so the core library is built for the target (needed for no_std/embedded targets and to avoid missing-sysroot build failures on matrix targets).

Docs: Correct the SECURITY.md supported versions table to list 0.1.x as supported (replacing the previous 0.2.x entry) to reflect the actual supported release series.

Author: swgiacomelli

.github/workflows/ci.yml

@@ -82,7 +82,7 @@ jobs:
           default: true
           ldproxy: false
       - uses: Swatinem/rust-cache@v2
-      - run: cargo +esp build --target ${{ matrix.target }}
+      - run: cargo +esp build --target ${{ matrix.target }} -Zbuild-std=core
 
   doc:
     name: Docs

SECURITY.md

@@ -4,8 +4,7 @@
 
 | Version | Supported |
 |---------|-----------|
-| 0.2.x   | Yes       |
-| < 0.2   | No        |
+| 0.1.x   | Yes       |
 
 ## Reporting a vulnerability