Remove unnecessary linker flag on libsyscommon.pc

Remove unnecessary linker flag on libsyscommon.pc

The linker flags pulled in by the variable SYSCOMMON_LIBS caused
problem when the libsyscommon was linked to another program. The
program might have located the libsyscommon by libsyscommon.pc.
Because of this, the program might have added linker flags
unintentionally that were, in fact, dependent to the libsyscommon,
not the program itself. And this causes build error like:
  ld: cannot find -lcynara-creds-pid: No such file or directory
The program didn't intend to link it to libcynara-creds-pid, and
therefore the rpmbuild would also not have installed the library.
But the linker flag -lcynara-creds-pid was pulled in by the
libsyscommon.pc, so it makes build error.

Change-Id: I81c2e4544f1c904527e4015aafb28ef0b2a659e9
Signed-off-by: Youngjae Cho <y0.cho@samsung.com>