Combining APPLE_COMMON_CRYPTO=1 and NO_OPENSSL=1 produces unexpected result

[Jack Nagel <jacknagel@gmail.com>]

When compiling git on OS X (where APPLE_COMMON_CRYPTO=1 is the
default) and specifying NO_OPENSSL=1, the resulting git uses the
BLK_SHA1 implementation rather than the functions available in
CommonCrypto.

$ uname -a
Darwin broadwell.local 15.0.0 Darwin Kernel Version 15.0.0: Sat Sep 19
15:53:46 PDT 2015; root:xnu-3247.10.11~1/RELEASE_X86_64 x86_64

$ make NO_OPENSSL=1
[...]
$ nm git | grep _SHA1_
0000000100173f00 t _blk_SHA1_Block
0000000100174e80 T _blk_SHA1_Final
000000010018fbb0 s _blk_SHA1_Final.pad
0000000100173de0 T _blk_SHA1_Init
0000000100173e10 T _blk_SHA1_Update

However, with OpenSSL available, it does use the CommonCrypto functions:

$ make
[...]
$ nm git | grep _SHA1_
                 U _CC_SHA1_Final
                 U _CC_SHA1_Init
                 U _CC_SHA1_Update

I would not expect the presence of NO_OPENSSL=1 to change the behavior
here, since neither case actually makes use of the OpenSSL SHA1
functions.