avoid unexpected output+behaviour when CDPATH is set

--- a/Admin/Isabelle_app/build	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/Isabelle_app/build	Mon May 17 13:57:19 2021 +1000
@@ -2,6 +2,7 @@
 
 set -e
 
+unset CDPATH
 THIS="$(cd "$(dirname "$0")"; pwd)"
 cd "$THIS"
 

--- a/Admin/bash_process/build	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/bash_process/build	Mon May 17 13:57:19 2021 +1000
@@ -2,6 +2,7 @@
 #
 # Multi-platform build script
 
+unset CDPATH
 THIS="$(cd "$(dirname "$0")"; pwd)"
 PRG="$(basename "$0")"
 

--- a/Admin/build	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/build	Mon May 17 13:57:19 2021 +1000
@@ -5,6 +5,7 @@
 ## directory layout
 
 if [ -z "$ISABELLE_HOME" ]; then
+  unset CDPATH
   ISABELLE_HOME="$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd ..; pwd)"
   ISABELLE_TOOL="$ISABELLE_HOME/bin/isabelle"
 fi

--- a/Admin/build_history	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/build_history	Mon May 17 13:57:19 2021 +1000
@@ -2,6 +2,7 @@
 #
 # DESCRIPTION: build history versions from another repository clone
 
+unset CDPATH
 THIS="$(cd "$(dirname "$0")"; pwd)"
 
 "$THIS/build" jars > /dev/null || exit $?

--- a/Admin/build_release	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/build_release	Mon May 17 13:57:19 2021 +1000
@@ -2,6 +2,7 @@
 #
 # DESCRIPTION: build full Isabelle distribution from repository
 
+unset CDPATH
 THIS="$(cd "$(dirname "$0")"; pwd)"
 
 "$THIS/build" jars || exit $?

--- a/Admin/cronjob/main	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/cronjob/main	Mon May 17 13:57:19 2021 +1000
@@ -2,6 +2,7 @@
 #
 # DESCRIPTION: start the main Isabelle cronjob
 
+unset CDPATH
 THIS="$(cd "$(dirname "$0")"; pwd)"
 
 source "$HOME/.bashrc"

--- a/Admin/init	Sun May 16 19:37:15 2021 +0200
+++ b/Admin/init	Mon May 17 13:57:19 2021 +1000
@@ -7,6 +7,7 @@
 
 ## environment
 
+unset CDPATH
 export ISABELLE_HOME="$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd ..; pwd)"
 
 ISABELLE_REPOS="https://isabelle.sketis.net/repos/isabelle"

--- a/bin/isabelle	Sun May 16 19:37:15 2021 +0200
+++ b/bin/isabelle	Mon May 17 13:57:19 2021 +1000
@@ -4,6 +4,8 @@
 #
 # Isabelle tool wrapper.
 
+unset CDPATH
+
 if [ -L "$0" ]; then
   TARGET="$(LC_ALL=C ls -l "$0" | sed 's/.* -> //')"
   exec "$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd "$(dirname "$TARGET")"; pwd)/$(basename "$TARGET")" "$@"

--- a/bin/isabelle_java	Sun May 16 19:37:15 2021 +0200
+++ b/bin/isabelle_java	Mon May 17 13:57:19 2021 +1000
@@ -4,6 +4,8 @@
 #
 # Isabelle/Java cold start -- without settings environment
 
+unset CDPATH
+
 if [ -L "$0" ]; then
   TARGET="$(LC_ALL=C ls -l "$0" | sed 's/.* -> //')"
   exec "$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd "$(dirname "$TARGET")"; pwd)/$(basename "$TARGET")" "$@"

--- a/bin/isabelle_scala_script	Sun May 16 19:37:15 2021 +0200
+++ b/bin/isabelle_scala_script	Mon May 17 13:57:19 2021 +1000
@@ -4,6 +4,8 @@
 #
 # Isabelle/Scala script wrapper.
 
+unset CDPATH
+
 if [ -L "$0" ]; then
   TARGET="$(LC_ALL=C ls -l "$0" | sed 's/.* -> //')"
   exec "$(cd "$(dirname "$0")"; cd "$(pwd -P)"; cd "$(dirname "$TARGET")"; pwd)/$(basename "$TARGET")" "$@"

--- a/src/Tools/Metis/fix_metis_license	Sun May 16 19:37:15 2021 +0200
+++ b/src/Tools/Metis/fix_metis_license	Mon May 17 13:57:19 2021 +1000
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+unset CDPATH
 THIS=$(cd "$(dirname "$0")"; echo $PWD)
 (cd $THIS;
  perl -p -i~ -w -e 's/MIT license/BSD License/g' Makefile src/*.s* scripts/mlpp)

--- a/src/Tools/Metis/make_metis	Sun May 16 19:37:15 2021 +0200
+++ b/src/Tools/Metis/make_metis	Mon May 17 13:57:19 2021 +1000
@@ -6,6 +6,7 @@
 # A few other ad hoc transformations are performed to ensure that the sources
 # compile within Isabelle on Poly/ML and SML/NJ.
 
+unset CDPATH
 THIS=$(cd "$(dirname "$0")"; echo $PWD)
 make -f Makefile.FILES refresh_FILES
 FILES=$(cat "$THIS/FILES")