ci: restore linux nasm install until mcpp#232 (lazy bootstrap ordering) is fixed

Author: Sunrisepeak

.github/workflows/validate.yml

@@ -218,6 +218,15 @@ jobs:
       # `xlings install nasm`), lazily, only when the plan has .asm units —
       # same self-bootstrap contract as the llvm toolchain. The sandbox copy
       # lands in ~/.mcpp/registry, so the cache carries it across runs.
+      # TEMPORARY belt-and-suspenders for compat.ffmpeg's NASM sources: the
+      # 0.0.95 lazy nasm self-bootstrap declares the build dead BEFORE the
+      # one-time bootstrap finishes (mcpp#232, 2x reproduced cold). PATH-first
+      # resolution makes this deterministic; drop once #232 is fixed.
+      - name: Install nasm (Linux)
+        if: runner.os == 'Linux'
+        shell: bash
+        run: sudo apt-get update && sudo apt-get install -y nasm
+
       - name: mcpp test --workspace
         shell: bash
         env: