Fix running teamcity builds when multiple configure flags are set

Summary:
The CONFIGURE_FLAGS variable has been quoted, which prevent the use of
space separated flags. This is the case when running the asan or ubsan
builds.

Test Plan:

ABC_BUILD_NAME=build-asan ./contrib/teamcity/build-configurations.sh

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D3974