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

["Tom G. Christensen" <tgc@jupiterrise.com>]

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