Unable to build on Linux Mint 18.2 (Ubuntu 16.04)

Greetings. Tying to build Watchman on Mint 18.2 and am met with the following error:

```
misutowolf@jsdev ~/projects/watchman $ make
make all-am
make[1]: Entering directory '/home/misutowolf/projects/watchman'
CXXLD watchman
watchman-ContentHash.o: In function `watchman::ContentHashCache::computeHashImmediate(watchman::ContentHashCacheKey const&) const':
/home/misutowolf/projects/watchman/ContentHash.cpp:65: undefined reference to `SHA1_Init'
/home/misutowolf/projects/watchman/ContentHash.cpp:78: undefined reference to `SHA1_Update'
/home/misutowolf/projects/watchman/ContentHash.cpp:81: undefined reference to `SHA1_Final'
collect2: error: ld returned 1 exit status
Makefile:1566: recipe for target 'watchman' failed
make[1]: *** [watchman] Error 1
make[1]: Leaving directory '/home/misutowolf/projects/watchman'
Makefile:1101: recipe for target 'all' failed
make: *** [all] Error 2
```
I noticed there was a similar issue raised regarding this error earlier, but the OP didn't mention his distro or anything.

Also, I've already installed `libssl-dev` and `libcrypto++-dev` on my system, and this build still fails. Not sure what else I could be missing here. Thanks in advance!