fix(ci): scope disableMarchNative to linux amd64 release builds (#1467)

## Summary

Refines the release workflow so `-d:disableMarchNative` is applied only
where needed: Linux amd64 release builds.

## Details

The previous workflow change passed `-d:disableMarchNative`
unconditionally to all `libstorage` builds, including macOS and Windows.
That is broader than necessary because the observed failure is specific
to secp256k1's x86_64 inline assembly when `-march=native` expands
against certain Linux amd64 CPUs.

This change:
- Computes platform-specific Nim flags once via a GitHub Actions step
output.
- Adds `-d:disableMarchNative` only for `matrix.os == linux` and
`matrix.cpu == amd64`.
- Reuses that platform flag for both the main release binary and
`libstorage`.
- Preserves `NIMFLAGS` exported by the Nimbus setup action, such as
Linux stack-usage flags and macOS OpenMP-related flags.
- Keeps `${{ env.nim_flags }}` scoped to the main binary build so
binary-specific flags do not leak into `libstorage`.
- Preserves the existing macOS `STORAGE_LIB_PARAMS` linker flag for
`libstorage`.

.github/workflows/release.yml

@@ -40,15 +40,15 @@ jobs:
     outputs:
       matrix: ${{ steps.matrix.outputs.matrix }}
     steps:
-    - name: Compute matrix
-      id: matrix
-      uses: fabiocaccamo/create-matrix-action@v5
-      with:
-        matrix: |
-          os {linux},   cpu {amd64}, builder {ubuntu-24.04},     nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
-          os {linux},   cpu {arm64}, builder {ubuntu-24.04-arm}, nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
-          os {macos},   cpu {arm64}, builder {macos-14},         nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
-          os {windows}, cpu {amd64}, builder {windows-latest},   nim_version {${{ env.nim_version }}}, shell {msys2}
+      - name: Compute matrix
+        id: matrix
+        uses: fabiocaccamo/create-matrix-action@v5
+        with:
+          matrix: |
+            os {linux},   cpu {amd64}, builder {ubuntu-24.04},     nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
+            os {linux},   cpu {arm64}, builder {ubuntu-24.04-arm}, nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
+            os {macos},   cpu {arm64}, builder {macos-14},         nim_version {${{ env.nim_version }}}, shell {bash --noprofile --norc -e -o pipefail}
+            os {windows}, cpu {amd64}, builder {windows-latest},   nim_version {${{ env.nim_version }}}, shell {msys2}
 
   # Build
   build:
@@ -104,16 +104,22 @@ jobs:
           echo "storage_binary=${storage_binary}" >>$GITHUB_ENV
           echo "c_bindings_lib=${c_bindings_lib}" >>$GITHUB_ENV
 
-      - name: Build Logos Storage binary
+      - name: Compute platform Nim flags
+        id: platform-nim-flags
+        shell: bash
         run: |
-          nim_flags="${{ env.nim_flags }}"
+          platform_nim_flags=""
           # secp256k1's x86_64 inline asm can hit a GCC register-allocation
           # failure when -march=native expands against this runner's CPU, so
           # pin a fixed baseline instead. arm64/macOS don't use that asm path.
           if [[ "${{ matrix.os }}" == "linux" && "${{ matrix.cpu }}" == "amd64" ]]; then
-            nim_flags="${nim_flags} -d:disableMarchNative"
+            platform_nim_flags="-d:disableMarchNative"
           fi
-          make NIMFLAGS="--out:${{ env.build_dir }}/${{ env.storage_binary }} ${nim_flags}"
+          echo "nim_flags=${platform_nim_flags}" >> "$GITHUB_OUTPUT"
+
+      - name: Build Logos Storage binary
+        run: |
+          make NIMFLAGS="${NIMFLAGS} --out:${{ env.build_dir }}/${{ env.storage_binary }} ${{ env.nim_flags }} ${{ steps.platform-nim-flags.outputs.nim_flags }}"
 
       - name: Package ${{ env.storage_binary_base }} Linux (compress and preserve perms)
         if: matrix.os == 'linux'
@@ -160,20 +166,20 @@ jobs:
         if: matrix.os == 'linux'
         run: |
           make -j${ncpu} update
-          make -j${ncpu} NIMFLAGS="-d:disableMarchNative" libstorage
+          make -j${ncpu} NIMFLAGS="${NIMFLAGS} ${{ steps.platform-nim-flags.outputs.nim_flags }}" libstorage
 
       - name: Build ${{ env.c_bindings_lib_base }} (MacOS)
         if: matrix.os == 'macos'
         run: |
           make -j${ncpu} update
-          STORAGE_LIB_PARAMS="--passL:\"-Wl,-install_name,@rpath/${{ env.c_bindings_lib_base }}.dylib\"" make -j${ncpu} NIMFLAGS="-d:disableMarchNative" libstorage
+          STORAGE_LIB_PARAMS="--passL:\"-Wl,-install_name,@rpath/${{ env.c_bindings_lib_base }}.dylib\"" make -j${ncpu} NIMFLAGS="${NIMFLAGS} ${{ steps.platform-nim-flags.outputs.nim_flags }}" libstorage
 
       - name: Build ${{ env.c_bindings_lib_base }} (Windows)
         if: matrix.os == 'windows'
         shell: msys2 {0}
         run: |
           make -j${ncpu} update
-          make -j${ncpu} NIMFLAGS="-d:disableMarchNative" libstorage
+          make -j${ncpu} NIMFLAGS="${NIMFLAGS} ${{ steps.platform-nim-flags.outputs.nim_flags }}" libstorage
 
       - name: Package ${{ env.c_bindings_lib_base }} Linux
         if: matrix.os == 'linux'