fix(boringssl-ci): inline NASM via choco in existing Windows toolchain steps

BoringSSL's CMakeLists.txt unconditionally calls
enable_language(ASM_NASM) on Windows regardless of target arch.
Linux/macOS runners ship nasm by default; Windows runners do not,
so cmake configure dies with "No CMAKE_ASM_NASM_COMPILER could be
found" on both win32-x64 and win32-arm64.

Add nasm to the existing `choco install` line in both Windows
toolchain steps (x64 + arm64-cross-compile) and append the choco
install dir to $GITHUB_PATH so cmake's enable_language probe finds
it.

Prior attempt added a standalone `ilammy/setup-nasm@SHA` step but
that produced repeated GHA startup_failure on dispatch (root cause
not isolated; reverted in 8509ed7 + 53e7c30). Inline choco install
matches the cmake/ccache/golang pattern that already works on these
runners.

Author: jdalton

.github/workflows/boringssl.yml

@@ -365,12 +365,16 @@ jobs:
         shell: bash
         run: |
           for i in 1 2 3; do
-            if choco install cmake mingw ccache golang -y; then
+            if choco install cmake mingw ccache golang nasm -y; then
               break
             fi
             echo "Attempt $i failed, retrying in 10 seconds..."
             sleep 10
           done
+          # choco installs nasm to `C:\Program Files\NASM` which isn't
+          # added to PATH automatically; cmake's enable_language(ASM_NASM)
+          # probes for `nasm` on PATH and dies if missing.
+          echo "C:\Program Files\NASM" >> $GITHUB_PATH
 
       - name: Setup build toolchain (Windows ARM64 cross-compile)
         if: |
@@ -380,12 +384,16 @@ jobs:
         shell: bash
         run: |
           for i in 1 2 3; do
-            if choco install cmake ccache golang -y; then
+            if choco install cmake ccache golang nasm -y; then
               break
             fi
             echo "Attempt $i failed, retrying in 10 seconds..."
             sleep 10
           done
+          # See Setup build toolchain (Windows x64) for why NASM path is
+          # added manually. ARM64 cross-compile path also calls
+          # enable_language(ASM_NASM) at cmake configure time.
+          echo "C:\Program Files\NASM" >> $GITHUB_PATH
 
       - name: Install llvm-mingw (Windows ARM64 cross-compile)
         if: |