Merge pthread into libc library

The pthread API is considered a standard feature of libc so better to
simply merge it with the libc. Pthreads are in fact already a part of
the libc in the form of weak symbols. This merger is also a prerequisite
for better integrating pthreads with the libc I/O task.

Fix #3054

repos/gems/src/server/tcp_terminal/target.mk

@@ -1,5 +1,5 @@
 TARGET = tcp_terminal
 SRC_CC = main.cc
-LIBS   = libc pthread libc_pipe
+LIBS   = libc libc_pipe
 
 CC_CXX_WARN_STRICT =