Windows package: fix random build failure due to race condition

The MEX files are built out-of-tree (because we want to do them in parallel).
This would create a potential race condition if several builds want to create
the symlinks under mex/matlab/ or mex/octave/.

The solution is to disable those symlinks for out-of-tree builds.

mex/build/matlab/mex.am

@@ -13,11 +13,15 @@ LIBS += $(MATLAB_LIBS)
 mexdir = $(libdir)/dynare/mex/matlab
 
 all-local: $(PROGRAMS)
-	$(MKDIR_P) $(top_srcdir)/../../matlab
+## Create symlinks in mex/matlab/, but only if the build is not
+## out-of-tree (because of the Windows installer)
+	if [ "$(abs_srcdir)" = "$(abs_builddir)" ]; then \
+		$(MKDIR_P) $(top_srcdir)/../../matlab && \
 		cd $(top_srcdir)/../../matlab && \
 		for p in $(PROGRAMS); do \
 			$(LN_S) -f $(abs_builddir)/$$p $$p; \
-	done
+		done; \
+	fi
 
 clean-local:
 	if test -d $(top_srcdir)/../../matlab; then \

mex/build/octave/mex.am

@@ -20,11 +20,15 @@ LIBS += $(shell $(MKOCTFILE) -p FLIBS)
 mexdir = $(libdir)/dynare/mex/octave
 
 all-local: $(PROGRAMS)
-	$(MKDIR_P) $(top_srcdir)/../../octave
+## Create symlinks in mex/octave/, but only if the build is not
+## out-of-tree (because of the Windows installer)
+	if [ "$(abs_srcdir)" = "$(abs_builddir)" ]; then \
+		$(MKDIR_P) $(top_srcdir)/../../octave && \
 		cd $(top_srcdir)/../../octave && \
 		for p in $(PROGRAMS); do \
 			$(LN_S) -f $(abs_builddir)/$$p $$p; \
-	done
+		done; \
+	fi
 
 clean-local:
 	if test -d $(top_srcdir)/../../octave; then \

windows/build.sh

@@ -220,8 +220,7 @@ cd "$ROOT_DIRECTORY"
 export TMP_DIRECTORY ROOT_DIRECTORY LIB32 LIB64 VERSION NTHREADS
 export -f "${TASKS[@]}"
 parallel "set -ex;shopt -s globstar;" ::: "${TASKS[@]}"
-# Clean up bogus symlinks left by parallel builds of MEX
-rm -f ../mex/matlab/*.mexw32 ../mex/matlab/*.mexw64 ../mex/octave/*.mex
+
 # Add supported_octave_version.m (see matlab/dynare.m)
 while read -r line
 do