It looks like Qt company has LGPLed versions tagged wich simplifies
things a bit while building, e.g. 5.15.3 current workaround matches
"v5.15.3-lts-lgpl" tag.
Background: Debian Sid is currently at Qt 5.15.8 which is impossible to
build from scratch with current script as only a few git versions are
tagged in the script format "v5.15.8".
Signed-off-by: Salvador Cuñat <salvador.cunat@gmail.com>
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