The error was introduced by dc96f667.
If `set -u` was called before sourcing greenplum_path.sh with bash, an
error `ZSH_VERSION: unbound variable` would be reported.
To solve the issue, use shell syntax `{:-}` which will output an empty
value if the variable doesn't exist.

Tested with zsh, bash and dash.

The generated greenplum_path.sh env file contained bash specific syntax
previously, so it errors out if the user's shell is zsh.

zsh doesn't have BASH_SOURCE. "${(%):-%x}" is the similar replacement
for zsh.
Also try to support other shells with some command combinations.
Tested with bash/zsh/dash.

Co-authored-by: NNing Wu <ningw@vmware.com>
Co-authored-by: NShaoqi Bai <bshaoqi@vmware.com>
Reviewed-by: NXin Zhang <zhxin@vmware.com>
Reviewed-by: NAdam Lee <adlee@vmware.com>
Reviewed-by: NHubert Zhang <hzhang@pivotal.io>
Reviewed-by: NJesse Zhang <sbjesse@gmail.com>

[#173046174]
Authored-by: NBradford D. Boyle <bradfordb@vmware.com>
(cherry picked from commit 28bcd4447551b3b9790e23d7865dbf403f79ef36)

Authored-by: NTingfang Bao <baotingfang@gmail.com>
(cherry picked from commit ae9bcdda4252524401fe6d1b4752355aa66e18ea)

Following the [Greenplum Server RPM Packaging Specification][0], we need
to update greenplum_path.sh file, and ensure many environment variables
set correct.

There are a few basic requirments for Greenplum Path Layer:

* greenplum-path.sh shall be installed to `${installation
  prefix}/greenplum-db-[package-version]/greenplum_path.sh`
* ${GPHOME} is set by given parameter, by default it should point to
  `%{installation prefix}/greenplum-db-devel`
* `${LD_LIBRARY_PATH}` shall be safely set to avoid a trailing colon
  (which will cause the linker to search the current directory when
  resolving shared objects)
* `${PYTHONPATH}` shall be set to `${GPHOME}/lib/python`
* `${PATH}` shall be set to `${GPHOME}/bin:${PATH}`
* If the file `${GPHOME}/etc/openssl.cnf` exists then `${OPENSSL_CONF}`
  shall be set to `${GPHOME}/etc/openssl.cnf`
* The greenplum_path.sh file shall pass [ShellCheck][1]

[0]: https://github.com/greenplum-db/greenplum-database-release/blob/master/Greenplum-Server-RPM-Packaging-Specification.md#detailed-package-behavior
[1]: https://github.com/koalaman/shellcheckAuthored-by: NTingfang Bao <bbao@pivotal.io>
(cherry picked from commit 5150237ac884227383f9f4f94e2383450756e7da)

This commit removes any reference to vendored python, formerly installed
in $GPHOME/ext/python.

Unvendoring python means that a system python of 2.7 is required.

In order to make this possible, several sub-fixes or testing scope fixes
are required:

- Python requirements should be installed globally using pip
- References to PYTHONHOME are removed
- PYTHONPATH becomes "$GPHOME/lib/python:${PYTHONPATH}"

GCC is no longer overridden as part of gpAux makefile process.

- Previously, gpAux Makefile overrode the $CC variable with the value
  "gcc". This obviously breaks convention which itself is a problem, but
  it is also broken because the top level Makefile and configure DO
  respect a CC variable being set.

- Setting CC="gcc" also means that gcc binary must be part of the user's
  path. This isn't a requirement or guarantee to compiling, so why keep
  this behavior?

- However, python packages should be compiled with the same GCC version
  that compiled system python - thus, we unset the "CC" variable when
  installing additional python libraries.
  Specifically, the configure args used to compile python are saved and
  re-used to compile libraries when the python setup.py build process is
  used. So if system python has different compiler flags than might be
  allowed in a newer version of gcc, the build of the libraries fails.
  This is specificaly of note when compiling python libraries in SLES,
  where the system python compiled with GCC 4.8 uses the
  `-fstack-clash-protection` flag, which is replaced by
  `-fstack-protector` in newer GCC versions. Thus, the configure args
   passed cause a failure to compile if a newer gcc version is used
   with "unrecognized command line option" error.

This does make significant improvements to simplify the code building
and testing framework:

- Patchelf requirements go away, as virtualenv is no longer necessary
- There is no need to copy system or other python into
  $GPHOME/etc/python

This commit does not address any of the following:

- Unvendoring individual python libraries, like psutil, pygresql, or
  yaml
- Updating any python code to work with python newer than 2.7
Co-authored-by: NTyler Ramer <tramer@pivotal.io>
Co-authored-by: NJamie McAtamney <jmcatamney@pivotal.io>

If no python in $GPHOME/ext/python/bin/python, $PYTHONHOME will be set
to empty string, which make python env wrong.
Signed-off-by: NTingfang Bao <bbao@pivotal.io>

- For centos and ubuntu, openssl.conf is from system default path
now. etc/openssl.conf in gpdb directory has been removed. So if we
should not export OPENSSL_CONF in greenplum_path.sh.

Rather than hardcoding to require /bin/bash, move to using a lookup
via "/usr/bin/env bash" to allow for greater portability of the code.
This also changes the Bash test to checking if the current shell is
actually Bash, rather than looking if bash is available on the file
system (since we by the above mentioned changes no longer need that).

- Remove Solaris special cases

- We don't support solaris anymore

- When PYTHONHOME is not set, don't use it.

- PYTHONHOME should remain default (unset) and not used as a variable,
unless a bundled python is available and preferred.

- Use LD_LIBRARY_PATH only
  since macos 10.5, LD_LIBRARY_PATH has been supported, so 
  remove conditionals for darwin, discarding DYLD_LIBRARY_PATH in favor of
  the standard LD_LIBRARY_PATH

1. copy *test/regress/*.pm file to install locaiton to support
regression test diff
2. set LIBPATH and GP_LIBPATH_FOR_PYTHON env for AIX
Signed-off-by: NPeifeng Qiu <pqiu@pivotal.io>