flush-cache: run it as a separate program, not using 'source'

That way it doesn't clutter up 'redo -x' as much.

t/deps/basic/test.do

@@ -1,10 +1,10 @@
 rm -f *.out *.log
 
-. ../../flush-cache.sh
+../../flush-cache.sh
 redo-ifchange 1.out 2.out
 [ "$(cat 1.log | wc -l)" = 1 ] || exit 55
 [ "$(cat 2.log | wc -l)" = 1 ] || exit 56
-. ../../flush-cache.sh
+../../flush-cache.sh
 touch 1.in
 redo-ifchange 1.out 2.out
 [ "$(cat 1.log | wc -l)" = 2 ] || exit 57

t/deps/dirtest/test.do

@@ -1,11 +1,11 @@
 rm -f log dir1/log dir1/stinky
 touch t1.do
-. ../../flush-cache.sh
+../../flush-cache.sh
 redo t1
 touch t1.do
-. ../../flush-cache.sh
+../../flush-cache.sh
 redo t1
-. ../../flush-cache.sh
+../../flush-cache.sh
 redo-ifchange t1
 C1="$(wc -l <dir1/log)"
 C2="$(wc -l <log)"

t/deps/doublestatic.do

@@ -3,7 +3,7 @@ rm -f static.log
 redo static1 static2
 
 touch static.in
-. ../flush-cache.sh
+../flush-cache.sh
 redo-ifchange static1 static2
 
 COUNT=$(wc -l <static.log)

t/deps/gentest.do

@@ -1,19 +1,19 @@
 rm -f genfile2 genfile2.do genfile.log
 
 echo echo hello >genfile2.do
-. ../flush-cache.sh
+../flush-cache.sh
 redo genfile1
 
 # this will cause a rebuild:
 #      genfile1 depends on genfile2 depends on genfile2.do
 rm -f genfile2.do
-. ../flush-cache.sh
+../flush-cache.sh
 redo-ifchange genfile1
 
 # but genfile2.do was gone last time, so genfile2 no longer depends on it.
 # thus, it can be considered up-to-date.  Prior versions of redo had a bug
 # where the dependency on genfile2.do was never dropped.
-. ../flush-cache.sh
+../flush-cache.sh
 redo-ifchange genfile1
 
 COUNT=$(wc -l <genfile.log)

t/deps/test1.do

@@ -6,6 +6,7 @@ if [ -e t1a ]; then
 else
 	BEFORE=
 fi
+../flush-cache.sh
 redo-ifchange t1a  # it definitely had to rebuild because t1dep changed
 AFTER="$(cat t1a)"
 if [ "$BEFORE" = "$AFTER" ]; then