chore: auto-detect TARGET_ARCH in cmake instead of hardcoding in preset

barretenberg/cpp/CMakePresets.json

@@ -19,7 +19,6 @@
       },
       "cacheVariables": {
         "CMAKE_BUILD_TYPE": "Release",
-        "TARGET_ARCH": "skylake",
         "ENABLE_PIC": "ON"
       }
     },

barretenberg/cpp/cmake/arch.cmake

@@ -5,7 +5,19 @@ if(WASM)
     add_compile_options(-fno-exceptions -fno-slp-vectorize)
 endif()
 
-if(NOT WASM AND NOT ARM AND TARGET_ARCH)
+# Auto-detect TARGET_ARCH if not explicitly set.
+# Use 'skylake' on x86_64 (matches our cross-compile presets) and 'generic' on ARM
+# to avoid emitting CPU-specific instructions (e.g. SVE on Graviton) that break on
+# other ARM machines like Apple Silicon.
+if(NOT WASM AND NOT TARGET_ARCH)
+    if(ARM)
+        set(TARGET_ARCH "generic")
+    else()
+        set(TARGET_ARCH "skylake")
+    endif()
+endif()
+
+if(NOT WASM AND TARGET_ARCH)
     message(STATUS "Target architecture: ${TARGET_ARCH}")
     add_compile_options(-march=${TARGET_ARCH})
 endif()

barretenberg/cpp/scripts/zig-c++.sh

@@ -1,15 +1,10 @@
 #!/bin/bash
 # Wrapper for zig c++ that pins glibc 2.35 on Linux (Ubuntu 22.04+ compat)
 # and uses native target on macOS.
-# On ARM64 Linux, we use an explicit aarch64 target instead of 'native' to produce
-# generic ARM64 code. This prevents CPU-specific instructions (e.g. SVE on Graviton)
-# from being emitted, ensuring binaries work across all ARM64 machines including
-# Apple Silicon in devcontainers.
+# Note: arch.cmake handles -march selection (skylake on x86, generic on ARM)
+# which overrides zig's native CPU detection, preventing CPU-specific instructions.
 if [[ "$(uname -s)" == "Linux" ]]; then
-  case "$(uname -m)" in
-    aarch64|arm64) exec zig c++ -target aarch64-linux-gnu.2.35 "$@" ;;
-    *)             exec zig c++ -target native-linux-gnu.2.35 "$@" ;;
-  esac
+  exec zig c++ -target native-linux-gnu.2.35 "$@"
 else
   exec zig c++ "$@"
 fi

barretenberg/cpp/scripts/zig-cc.sh

@@ -1,15 +1,10 @@
 #!/bin/bash
 # Wrapper for zig cc that pins glibc 2.35 on Linux (Ubuntu 22.04+ compat)
 # and uses native target on macOS.
-# On ARM64 Linux, we use an explicit aarch64 target instead of 'native' to produce
-# generic ARM64 code. This prevents CPU-specific instructions (e.g. SVE on Graviton)
-# from being emitted, ensuring binaries work across all ARM64 machines including
-# Apple Silicon in devcontainers.
+# Note: arch.cmake handles -march selection (skylake on x86, generic on ARM)
+# which overrides zig's native CPU detection, preventing CPU-specific instructions.
 if [[ "$(uname -s)" == "Linux" ]]; then
-  case "$(uname -m)" in
-    aarch64|arm64) exec zig cc -target aarch64-linux-gnu.2.35 "$@" ;;
-    *)             exec zig cc -target native-linux-gnu.2.35 "$@" ;;
-  esac
+  exec zig cc -target native-linux-gnu.2.35 "$@"
 else
   exec zig cc "$@"
 fi