build-pkg pkg-name of std pkg causes rt build failure

[Scott Little]

Title
-----
build-pkg pkg-name of std pkg causes rt build failure

Brief Description
-----------------
Designer issues 'build-pkg pkg-name' where pkg-name is only valid for std builds.

Expected result is that only 'std' build is executed on the named package.
What is observed is that aftes a successful std build, an 'rt' build is
executed with an invalid package list causing a failure.

The package is built correctly, but command returns 1.
This breaks scripts that test build-pkgs return code.

Severity
--------
Major

Steps to Reproduce
------------------
build-pkg shim-signed
echo $?

Expected Behavior
------------------
No rt build attempt, and return code 0

Actual Behavior
----------------
An unneeded rt build attemp after the std build.
rt build failes due to invalid target.
Final return code is 1.

Reproducibility
---------------
100%

System Configuration
--------------------
N/A

Branch/Pull Time/Commit
-----------------------
master
stx-root: b20ac0164dd830eda64426b076322d7ac9365d20

build-pkgTimestamp/Logs
--------------
15:46:26 build-rpms-parallel --std --no-descendants --no-build-info --no-required --careful shim-signed
15:46:26 ALL=0
15:46:42 Find the list of packages we must compile
15:46:42 waiting
15:46:42 Including named target '/localdisk/loadbuild/jenkins/Titanium_R6_build/2018-09-25_12-49-42/std/rpmbuild/SPECS/shim-signed-12-1.tis.2.src.rpm/NAMES/shim-signed'
15:46:42 Including named target '/localdisk/loadbuild/jenkins/Titanium_R6_build/2018-09-25_12-49-42/std/rpmbuild/SPECS/shim-signed-12-1.tis.2.src.rpm/BUILDS/shim-signed'
15:46:42 found shim-signed: /localdisk/loadbuild/jenkins/Titanium_R6_build/2018-09-25_12-49-42/std/rpmbuild/SRPMS/shim-signed-12-1.tis.2.src.rpm
15:46:42 SRPMS_TO_COMPILE = shim-signed
...
15:52:44 Pkgs built: 1
15:52:44 Packages successfully built in this order:
15:52:44 /localdisk/loadbuild/jenkins/Titanium_R6_build/2018-09-25_12-49-42/std/rpmbuild/SRPMS/shim-signed-12-1.tis.2.src.rpm
...
15:53:34 build-srpms-parallel --rt --no-descendants --no-build-info
15:53:34 make: all
...
15:53:44 ERROR: reaper (1286): Failed to build src.rpm from source at 'b2'
15:53:44

######## Tue Sep 25 15:53:44 EDT 2018: build-srpm-parallel --rt failed with rc=1

Tue Sep 25 15:53:44 EDT 2018: build-srpm-parallel --rt failed with rc=1

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/605458

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/605458
Committed: https://git.openstack.org/cgit/openstack/stx-root/commit/?id=91f3b6f899776cbb9f5bc85a7c1dfe96dc261927
Submitter: Zuul
Branch: master

commit 91f3b6f899776cbb9f5bc85a7c1dfe96dc261927
Author: Scott Little <email address hidden>
Date: Wed Sep 26 11:06:40 2018 -0400

    build-pkg pkg-name of std pkg causes rt build failure

    Brief Description
    -----------------
    Designer issues 'build-pkg pkg-name' where pkg-name is only valid for
    std builds.

    Expected result is that only 'std' build is executed on the named
    package.
    What is observed is that aftes a successful std build, an 'rt' build is
    executed with an invalid package list causing a failure.

    The package is built correctly, but command returns 1.
    This breaks scripts that test build-pkgs return code.

    Problem
    -------
    find_targets returned $EMPTY_LIST rather than $EMPTY_TARGETS as expected.

    Solution
    --------
    find_targets must return $EMPTY_TARGETS when no targets are found for
    the build type.

    Closes-Bug: 1794542
    Change-Id: I3d21bb793b1fc9637b16a08fdfcd2fd998742bfb
    Signed-off-by: Scott Little <email address hidden>