diff --git a/build.py b/build.py
index f07775e3..d92c3845 100644
--- a/build.py
+++ b/build.py
@@ -227,6 +227,7 @@ if not glob("../fluxengine-testdata/data"):
     print("fluxengine-testdata not found; skipping corpus tests")
 else:
     corpus = [
+        ("acorndfs", "", "--200"),
         ("agat", "", ""),
         ("amiga", "", ""),
         ("apple2", "", "--140 40track_drive"),
diff --git a/build/ab.py b/build/ab.py
index 27654568..d5393867 100644
--- a/build/ab.py
+++ b/build/ab.py
@@ -417,8 +417,6 @@ def export(self, name=None, items: TargetsMap = {}, deps: Targets = []):
     for dest, src in items.items():
         destf = filenameof(dest)
         dir = dirname(destf)
-        if dir:
-            cs += ["mkdir -p " + dir]
 
         srcs = filenamesof(src)
         if len(srcs) != 1:
@@ -426,13 +424,16 @@ def export(self, name=None, items: TargetsMap = {}, deps: Targets = []):
                 "a dependency of an export must have exactly one output file"
             )
 
-        cs += ["cp %s %s" % (srcs[0], destf)]
+        emitter_rule(self.name + "+" + destf, srcs, [destf])
+        emitter_label(f"CP {destf}")
+        if dir:
+            emitter_exec(["mkdir -p " + dir])
+
+        emitter_exec(["cp %s %s" % (srcs[0], destf)])
         self.outs += [destf]
 
-    emitter_rule(self.name, items.values(), self.outs, deps)
-    emitter_label(f"EXPORT {self.name}")
-
-    emitter_exec(cs)
+    emitter_rule(self.name, self.outs, [], deps)
+    emit("\t@")
 
     if self.outs:
         emit("clean::")
diff --git a/build/pkg.py b/build/pkg.py
index c1c98f47..e6a10bb3 100644
--- a/build/pkg.py
+++ b/build/pkg.py
@@ -6,7 +6,9 @@ import subprocess
 emit(
     """
 PKG_CONFIG ?= pkg-config
-PACKAGES := $(shell $(PKG_CONFIG) --list-all | cut -d' ' -f1)
+PACKAGES := $(shell $(PKG_CONFIG) --list-all | cut -d' ' -f1 | sort)
+PCFILES := $(wildcard $(patsubst %,%/*.pc,$(subst :, ,$(shell $(PKG_CONFIG) --variable pc_path pkg-config))))
+$(OBJ)/build.mk: $(PCFILES)
 """
 )
 
diff --git a/src/gui/build.py b/src/gui/build.py
index a7118161..f2d85c23 100644
--- a/src/gui/build.py
+++ b/src/gui/build.py
@@ -6,11 +6,12 @@ emit(
     """
 WX_CONFIG ?= wx-config
 ifneq ($(strip $(shell command -v $(WX_CONFIG) >/dev/null 2>&1; echo $$?)),0)
-$(error Required binary 'wx-config' not found.)
-endif
-
+WX_CFLAGS = $(error Required binary 'wx-config' not found.)
+WX_LDFLAGS = $(error Required binary 'wx-config' not found.)
+else
 WX_CFLAGS := $(shell $(WX_CONFIG) --cxxflags core base adv aui richtext)
 WX_LDFLAGS := $(shell $(WX_CONFIG) --libs core base adv aui richtext)
+endif
 """
 )