fix eclipse problem rename core.a to arduino.ar

see esp8266#948

Author: Links2004

platform.txt

@@ -64,10 +64,10 @@ recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpreprocessor
 recipe.S.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.cpreprocessor.flags} {compiler.S.flags} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.c.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}"
 
 ## Create archives
-recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{build.path}/core.a" "{object_file}"
+recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{build.path}/arduino.ar" "{object_file}"
 
 ## Combine gc-sections, archives, and objects
-recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" -Wl,--start-group {object_files} "{build.path}/core.a" {compiler.c.elf.libs} -Wl,--end-group  "-L{build.path}"
+recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" -Wl,--start-group {object_files} "{build.path}/arduino.ar" {compiler.c.elf.libs} -Wl,--end-group  "-L{build.path}"
 
 ## Create eeprom
 recipe.objcopy.eep.pattern=