From xcodebuild manual page:
xcodebuild [-project projectname] [-target targetname ...] [-configuration configurationname] [-sdk [sdkfullpath | sdkname]] [buildaction ...] [setting=value ...] [-userdefault=value ...]
and build action could take following values (UPD 13.08.2018):
action ...
Specify one or more actions to perform. Available actions are:
build Build the target in the build root (SYMROOT). This is the default action, and
is used if no action is given.
build-for-testing Build the target and associated tests in the build root (SYMROOT). This will
also produce an xctestrun file in the build root. This requires specifying a
scheme.
analyze Build and analyze a target or scheme from the build root (SYMROOT). This
requires specifying a scheme.
archive Archive a scheme from the build root (SYMROOT). This requires specifying a
scheme.
test Test a scheme from the build root (SYMROOT). This requires specifying a
scheme and optionally a destination.
test-without-building Test compiled bundles. If a scheme is provided with -scheme then the command
finds bundles in the build root (SRCROOT). If an xctestrun file is provided
with -xctestrun then the command finds bundles at paths specified in the
xctestrun file.
install-src Copy the source of the project to the source root (SRCROOT).
install Build the target and install it into the target's installation directory in
the distribution root (DSTROOT).
clean Remove build products and intermediate files from the build root (SYMROOT).
In your case
xcodebuild -sdk "${TARGET_SDK}" -xcconfig "${CONFIG_FILE_PATH}" -configuration Release clean build
There are two build actions in this command line: 'clean' and 'build'. The 'clean' action is performed first, then the 'build'. As the documentation states, you can specify multiple build actions in a command, and doing so rather than using separate commands ensures that the other options are the same for all the build actions.