prevent sourced files from leaking unintended state to callers

scripts/build/generate-version.sh

@@ -8,3 +8,5 @@
 LAST_COMMIT_TIMESTAMP=$(git log -1 --format=%ct)
 export DOTNET_BUILD_VERSION=1.0.0-dev-$LAST_COMMIT_TIMESTAMP
 echo "Version: $DOTNET_BUILD_VERSION"
+
+unset LAST_COMMIT_TIMESTAMP

scripts/common/_common.sh

@@ -9,15 +9,15 @@ while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symli
   COMMONSOURCE="$(readlink "$COMMONSOURCE")"
   [[ $COMMONSOURCE != /* ]] && COMMONSOURCE="$COMMONDIR/$COMMONSOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
 done
-DIR="$( cd -P "$( dirname "$COMMONSOURCE" )" && pwd )"
+COMMONDIR="$( cd -P "$( dirname "$COMMONSOURCE" )" && pwd )"
 
-source "$DIR/_clang.sh"
-source "$DIR/_prettyprint.sh"
-source "$DIR/_rid.sh"
+source "$COMMONDIR/_clang.sh"
+source "$COMMONDIR/_prettyprint.sh"
+source "$COMMONDIR/_rid.sh"
 
 # TODO: Replace this with a dotnet generation
 export TFM=dnxcore50
-export REPOROOT=$(cd $DIR/../.. && pwd)
+export REPOROOT=$(cd $COMMONDIR/../.. && pwd)
 export OUTPUT_ROOT=$REPOROOT/artifacts/$RID
 export DNX_DIR=$OUTPUT_ROOT/dnx
 export DNX_ROOT=$DNX_DIR/bin
@@ -30,8 +30,5 @@ export HOST_DIR=$OUTPUT_ROOT/corehost
 [ -z "$DOTNET_HOME" ] && export DOTNET_HOME=$STAGE2_DIR && export PATH=$STAGE2_DIR/bin:$PATH
 [ -z "$CONFIGURATION" ] && export CONFIGURATION=Debug   
 
-# if the conditional set is the last command in this file AND 
-# the condition is false then the program exits here. Seems like
-# a bug in BASH... or indication that there is more to learn about Linux
-# the below line is a hack that works around this issue
-a=1+1
+unset COMMONSOURCE
+unset COMMONDIR