Gracefully handle the case when a DISTDIR already exists

qa/pull-tester/build-tests.sh.in

@@ -9,7 +9,7 @@ set -o xtrace
 
 MINGWPREFIX=$1
 JAVA_COMPARISON_TOOL=$2
-RUN_LARGE_REORGS=$3
+RUN_EXPENSIVE_TESTS=$3
 JOBS=${4-1}
 OUT_DIR=${5-}
 
@@ -23,17 +23,22 @@ DISTDIR=@PACKAGE@-@VERSION@
 # Cross-compile for windows first (breaking the mingw/windows build is most common)
 cd @abs_top_srcdir@
 make distdir
-mv $DISTDIR win32-build
+mkdir -p win32-build
+rsync -av $DISTDIR/ win32-build/
+rm -r $DISTDIR
 cd win32-build
+
 ./configure --disable-silent-rules --disable-ccache --prefix=$MINGWPREFIX --host=i586-mingw32msvc --with-qt-bindir=$MINGWPREFIX/host/bin --with-qt-plugindir=$MINGWPREFIX/plugins --with-qt-incdir=$MINGWPREFIX/include --with-boost=$MINGWPREFIX --with-protoc-bindir=$MINGWPREFIX/host/bin CPPFLAGS=-I$MINGWPREFIX/include LDFLAGS=-L$MINGWPREFIX/lib
 make -j$JOBS
 
 # And compile for Linux:
 cd @abs_top_srcdir@
 make distdir
-mv $DISTDIR linux-build
+mkdir -p linux-build
+rsync -av $DISTDIR/ linux-build/
+rm -r $DISTDIR
 cd linux-build
-if [ $RUN_LARGE_REORGS = 1 ]; then
+if [ $RUN_EXPENSIVE_TESTS = 1 ]; then
   ./configure --disable-silent-rules --disable-ccache --with-comparison-tool="$JAVA_COMPARISON_TOOL" --enable-comparison-tool-reorg-tests
 else
   ./configure --disable-silent-rules --disable-ccache --with-comparison-tool="$JAVA_COMPARISON_TOOL"