Attempt to fix boringssl tests

Commit abe256e7 changed the config target
element from 'cxx' to 'CXX'; catch up accordingly.
Also use a space to offset the template boundary, per convention.

[extended tests]
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5577)

test/ossl_shim/build.info

-IF[{- defined $target{cxx} && !$disabled{"external-tests"}-}]
+IF[{- defined $target{CXX} && !$disabled{"external-tests"} -}]
   PROGRAMS_NO_INST=ossl_shim
   SOURCE[ossl_shim]=ossl_shim.cc async_bio.cc packeted_bio.cc test_config.cc
   INCLUDE[ossl_shim]=. include ../../include