chore: Run js build with two builders

Author: spotandjake

compiler/esy.json

@@ -25,7 +25,7 @@
     "copy:exe": "cp -f #{$GRAINC_BIN_PATH} #{$GRAINDOC_BIN_PATH} #{$GRAINFORMAT_BIN_PATH} #{$GRAINLSP_BIN_PATH} #{$CLI_BIN_DIR}",
     "copy:js": "cp -f #{$GRAINC_JS_PATH} #{$GRAINDOC_JS_PATH} #{$GRAINFORMAT_JS_PATH} #{$GRAINLSP_JS_PATH}  #{$CLI_BIN_DIR}",
     "clean": "rm -rf #{self.root}/_esy",
-    "build:js": "esy b dune build @js --no-buffer #{os == 'windows' ? '-j 2' : ''}",
+    "build:js": "esy b dune build @js --no-buffer #{os != 'darwin' ? '-j 2' : ''}",
     "test": "#{$TEST_EXEC_PATH}",
     "test:js": "node #{$TEST_JS_PATH}",
     "format": "dune build @fmt --auto-promote",