Avoid adding linker flags as make targets

Signed-off-by: Travis Cross <tc@traviscross.com>

FS-353
Allow a system provided version of pcre to be used

Signed-off-by: Travis Cross <tc@traviscross.com>

FS-353
FS-5681 --resolve
Allow a system provided version of Speex to be used

Signed-off-by: Travis Cross <tc@traviscross.com>

FS-353