Hardcoded #!/bin/sh in t5532 causes problems on Solaris

Hello,

Looking at the testsuite results on Solaris I see a failure in t5532.3.

Running the testsuite with -v -i revealed a shell syntax error:

proxying for example.com 9418 ./proxy: syntax error at line 3: `cmd=$' unexpected not ok 3 - fetch through proxy works # # git fetch fake && # echo one >expect && # git log -1 --format=%s FETCH_HEAD >actual && # test_cmp expect actual #

Looking a t5532-fetch-proxy.sh the problem is obvious, it writes out a helper script which explicitly uses #!/bin/sh but fails to take into account that systems like Solaris has an ancient /bin/sh that knows nothing about POSIX things like $(). Replacing $() with `` was enough to make the test pass.

-tgc