pgsql: Don't use an Msys virtual path to create a tablespace

Don't use an Msys virtual path to create a tablespace

The new unlogged_reinit recovery tests create a new tablespace using
TestLib.pm's tempdir. However, on msys that function returns a virtual
path that isn't understood by Postgres. Here we add a new function to
TestLib.pm to turn such a path into a real path on the underlying file
system, and use it in the new test to create the tablespace. The new
function is essentially a NOOP everywhere but msys.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9ad21a6957ff2d8743e9a59ba062d3c009b24ec4

Modified Files
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src/test/perl/TestLib.pm                   | 18 ++++++++++++++++++
src/test/recovery/t/014_unlogged_reinit.pl |  4 +++-
2 files changed, 21 insertions(+), 1 deletion(-)