explicitly disable use of MySQL in recent GDAL easyconfigs

[branfosj]

(created using eb --new-pr)

In the output of ldd $EBROOTGDAL/lib64/libgdal.so for GDAL without this change we have

        libmariadb.so.3 => /lib64/libmariadb.so.3 (0x00007f7b74835000)

On the node we built GDAL on

$ ls -l /usr/lib64/libmysqlclient.so
lrwxrwxrwx 1 root root 15 Dec  3  2020 /usr/lib64/libmysqlclient.so -> libmariadb.so.3

And in the build log we have

-- Found MySQL: /usr/lib64/libmysqlclient.so (found version "")

With this change we do not have the linkage to libmariadb.so.3 and

-- Disabled components:

 * MYSQL component has been detected, but is disabled with GDAL_USE_MYSQL=OFF

[branfosj]

Test report by @branfosj
SUCCESS
Build succeeded for 3 out of 3 (3 easyconfigs in total)
bear-pg0105u03a - Linux RHEL 8.6, x86_64, Intel(R) Xeon(R) Platinum 8360Y CPU @ 2.40GHz (icelake), Python 3.6.8
See https://gist.github.com/branfosj/3278032f7079567e4ae3e21095b43113 for a full test report.

[jfgrimm]

Test report by @jfgrimm
SUCCESS
Build succeeded for 26 out of 26 (3 easyconfigs in total)
node019.viking2.yor.alces.network - Linux Rocky Linux 8.9, x86_64, AMD EPYC 7643 48-Core Processor, Python 3.6.8
See https://gist.github.com/jfgrimm/219520083b6fc2c772c321ca43655138 for a full test report.

[jfgrimm]

lgtm

[jfgrimm]

Going in, thanks @branfosj!