Preserve buffetfsm binary on make clean

The Dockerfile in this repo deletes the llvm build files after building
buffet, which means it cannot be rebuilt inside the running container.

- This commit allows zcc to continue without rebuilding buffet, if an
existing buffetfsm binary is available.

- This commit also prevents the buffetfsm binary from being blown away
on running `make clean` in the pepper directory.

compiler/zcc

@@ -165,7 +165,15 @@ if [ "$extension" == "c" ]; then
           if [ $? != 0 ]; then
           {
               echo "Failed to build FSM transformer. Please make sure you have compiled LLVM."
-              exit 1
+
+              if [ ! -f buffetfsm ]; then
+              {
+                echo "FSM transformer not found. Terminating"
+                exit 1
+              }
+              else
+                echo "Found existing FSM transformer binary. Continuing without recompilation."
+              fi
           } fi
 
           cd ..

install_buffet.sh

@@ -7,3 +7,8 @@ mkdir llvm-build
 cd llvm-build
 $PWD/../llvm/configure --prefix=$PWD/../toolchain --enable-shared --enable-optimized
 make -j$(nproc)
+
+# The commands below build the actual loop transformer binary.
+
+cd ..
+make

pepper/Makefile

@@ -176,7 +176,6 @@ clean:
 	rm -f ../compiler/backend/tmptime
 	rm -f ../compiler/tmptime
 	cd ../compiler/frontend; make clean; 
-	cd ../compiler/buffetfsm; make clean;
 
 gadget%: ext_gadget_bridge.cpp
-	$(CXX) $(CXXFLAGS) -UBINARY_OUTPUT -DNAME=\"$(TARG)\" $(IFLAGS)  $<  -o $(BINDIR)/$@ $(COMMON_LIB_OBJFILES) $(LDFLAGS)
+	$(CXX) $(CXXFLAGS) -UBINARY_OUTPUT -DNAME=\"$(TARG)\" $(IFLAGS)  $<  -o $(BINDIR)/$@ $(COMMON_LIB_OBJFILES) $(LDFLAGS)