Build and use libraries locally in the nacl build, not requiring "partial SDK"

src/untrusted/irt_stub/nacl.scons

 # -*- python -*-
 # Copyright (c) 2011 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 Import('env')
 
 env.ComponentLibrary('libppapi_stub', [
     'ppapi_plugin_main.c',
     'ppapi_plugin_start.c',
     'plugin_main_irt.c',
     'thread_creator.c'
     ])
-env.AddLibraryToSdk(['libppapi_stub'])
-env.AddObjectToSdk(['libppapi.a'])
-
-if not env.Bit('nacl_disable_shared'):
-  env.AddObjectToSdk(['libppapi.so'])
+lib = env.AddLibraryToSdk(['libppapi_stub'])
 
 gap_env = env.Clone()
 gap_env.Append(CPPDEFINES=[
     ['IRT_DATA_REGION_START', '${IRT_DATA_REGION_START}']
     ])
 if gap_env.Bit('bitcode'):
   # This is not actually a platform-specific, it's generic to any assembler
   # for an ELF target.  But it can't be compiled to LLVM bitcode.
   gap_env.Replace(OBJSUFFIX='.o')
   gap_env.Append(ASFLAGS=['-arch', '${TARGET_FULLARCH}'])
 
 link_segment_gap = gap_env.ComponentObject(
     'link_segment_gap',
     '${SCONSTRUCT_DIR}/src/untrusted/irt/link_segment_gap.S'
     )
-gap_env.AddObjectToSdk(link_segment_gap, is_platform=True)
+gap_obj = gap_env.AddObjectToSdk(link_segment_gap, is_platform=True)
+
+static_script = env.AddObjectToSdk(['libppapi.a'])
+
+# Anything that links with -lppapi (i.e. ${PPAPI_LIBS}) needs not just the
+# libppapi.a or libppapi.so linker script file, but also the object and
+# library it refers to.  By telling scons that libppapi.a depends on these
+# objects, we ensure that it builds them before something using ${PPAPI_LIBS}.
+script_deps = [gap_obj, lib]
+env.Depends(static_script, script_deps)
+
+# The static libppapi.a refers to libpthread.a, and in the non-glibc
+# build, we are the one providing that too.
+if not env.Bit('nacl_glibc'):
+  env.Depends(static_script, env.File('${LIB_DIR}/libpthread.a'))
+
+if not env.Bit('nacl_disable_shared'):
+  dyn_script = env.AddObjectToSdk(['libppapi.so'])
+  env.Depends(dyn_script, script_deps)