[spec/redirect] Work around flakiness.

This is issue #330.  For some reason mksh started being flaky in
parallel ('osh-all'), but not when run serially on its own.

[build] Get rid of /../ in path.

This caused the ovm-build benchmark to fail for some unknown reason.

build/common.sh

@@ -8,14 +8,16 @@ set -o errexit
 #
 # TODO: It would be much nicer to export a FUNCTION "cxx" rather than a
 # variable $CXX.
-_THIS_DIR=$(dirname ${BASH_SOURCE[0]})
+_THIS_DIR=$(dirname ${BASH_SOURCE[0]})  # oilshell/oil/build/ dir
 readonly _THIS_DIR
+_REPO_ROOT=$(cd $THIS_DIR/.. && pwd)  # oilshell/oil
+readonly _REPO_ROOT
 
 # TODO: This changes depending on the version.  Maybe there should be a 'clang'
 # function for things that really require clang, like code coverage and so
 # forth.
 readonly CLANG_DIR_RELATIVE='_deps/clang+llvm-5.0.1-x86_64-linux-gnu-ubuntu-16.04'
-readonly CLANG_DIR=$_THIS_DIR/../$CLANG_DIR_RELATIVE
+readonly CLANG_DIR=$_REPO_ROOT/$CLANG_DIR_RELATIVE
 readonly CLANG=$CLANG_DIR/bin/clang
 readonly CLANGXX=$CLANG_DIR/bin/clang++
 

spec/redirect.test.sh

@@ -194,8 +194,13 @@ true 9> "$TMP/fd.txt"
 cat "$TMP/fd.txt"
 ## stdout-json: ""
 
-#### : 3>&3 (OSH regression)
-: 3>&3
+#### : 4>&4 (OSH regression)
+
+# Note: This used to be 3>&3 except on the 0.8.5 release it was flaky under
+# mksh only?  Reproducible with test/spec.sh osh-all, but not test/spec.sh
+# redirect.  Very weird.
+
+: 4>&4
 echo hello
 ## stdout: hello
 ## BUG mksh stdout-json: ""