avoid request stalls during proactive rebuilds

scripts/compile_wasm_unit

@@ -15,6 +15,7 @@ ABI_VERSION=${UCE_UNIT_ABI_VERSION:-6}
 ROOT=$(pwd)
 OBJ_FN="$DEST_DIR/$PP_FN.wasm.o"
 ABI_TMP="$DEST_DIR/$PP_FN.uce-abi.txt"
+WASM_TMP="$DEST_DIR/$WASM_FN.tmp.$$"
 PCH_ENABLED=${UCE_WASM_UNIT_PCH:-1}
 PCH_DIR=${UCE_WASM_PCH_DIR:-/tmp/uce/wasm-w2/pch}
 COMMON_FLAGS=(
@@ -44,6 +45,7 @@ PCH_KEY=$(printf '%s\n%s\n%s\n%s\n' "$ABI_VERSION" "$TOOLCHAIN_ID" "$HEADER_HASH
 PCH_FN="$PCH_DIR/uce_lib-wasm-unit-$PCH_KEY.pch"
 
 mkdir -p "$DEST_DIR" >/dev/null 2>&1
+trap 'rm -f "$OBJ_FN" "$ABI_TMP" "$WASM_TMP"' EXIT
 
 build_pch_if_needed() {
 	if [ "$PCH_ENABLED" = "0" ]; then
@@ -80,7 +82,7 @@ fi
 "$SDK/bin/wasm-ld" -shared --experimental-pic \
 	--unresolved-symbols=import-dynamic \
 	--Bsymbolic \
-	"$OBJ_FN" -o "$DEST_DIR/$WASM_FN" \
+	"$OBJ_FN" -o "$WASM_TMP" \
 	--export-if-defined=__uce_set_current_request \
 	--export-if-defined=__uce_render \
 	--export-if-defined=__uce_component \
@@ -90,8 +92,9 @@ fi
 	--export-if-defined=__uce_once \
 	--export-if-defined=__uce_init
 
-"$SDK/bin/llvm-objcopy" --add-section=uce.abi="$ABI_TMP" "$DEST_DIR/$WASM_FN"
+"$SDK/bin/llvm-objcopy" --add-section=uce.abi="$ABI_TMP" "$WASM_TMP"
 
-python3 scripts/check_unit_wasm.py "$DEST_DIR/$WASM_FN" --abi-version "$ABI_VERSION" --llvm-nm "$SDK/bin/llvm-nm"
+python3 scripts/check_unit_wasm.py "$WASM_TMP" --abi-version "$ABI_VERSION" --llvm-nm "$SDK/bin/llvm-nm"
+mv "$WASM_TMP" "$DEST_DIR/$WASM_FN"
 
 rm -f "$OBJ_FN" "$ABI_TMP"