fix(build): Source common env.sh in wxuniversal build script

Ensures EMSDK_PYTHON is set correctly for Emscripten 4.0.22+ which
requires explicit Python path configuration.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/build-wxuniversal-wasm.sh

@@ -3,6 +3,9 @@
 
 # Redirect all output to a log file (re-execs script with redirection)
 source "$(dirname "$0")/common/logging.sh"
+
+# Source common environment (sets up EMSDK_PYTHON for Emscripten 4.0.22+)
+source "$(dirname "$0")/common/env.sh"
 # This builds the GUI-enabled wxWidgets needed for KiCad
 #
 # Prerequisites: