avoid exporting __assert_func symbol from system lib

__assert_func and its dependencies are automatically added by libc unless we provide a stub implementation and avoid uisng -Wl,--whole-archive when linking against system lib

Author: facchinm

Diff for: cores/arduino/abi.cpp

@@ -21,6 +21,12 @@
 extern "C" void __cxa_pure_virtual(void) __attribute__ ((__noreturn__));
 extern "C" void __cxa_deleted_virtual(void) __attribute__ ((__noreturn__));
 
+extern "C" void __assert_func(void) __attribute__ ((__noreturn__));
+
+void __assert_func(void) {
+    while (1)
+    ;
+}
 
 void __cxa_pure_virtual(void) {
   // We might want to write some diagnostics to uart in this case

Diff for: platform.txt

@@ -68,7 +68,7 @@ recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -D
 recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{archive_file_path}" "{object_file}"
 
 ## Combine gc-sections, archives, and objects
-recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} "-T{build.variant.path}/{build.ldscript}" "-Wl,-Map,{build.path}/{build.project_name}.map" {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" "-L{build.path}" "-L{build.variant.path}" -Wl,--whole-archive "-l{build.variant_system_lib}" -Wl,--no-whole-archive -Wl,--start-group "-l{build.variant_system_lib}" -lnsim -lc -lm -lgcc {object_files} "{build.path}/{archive_file}"
+recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} "-T{build.variant.path}/{build.ldscript}" "-Wl,-Map,{build.path}/{build.project_name}.map" {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" "-L{build.path}" "-L{build.variant.path}" -Wl,--no-whole-archive -Wl,--start-group -lnsim -lc -lm -lgcc -l{build.variant_system_lib} {object_files} "{build.path}/{archive_file}"
 
 ## Save output with debug symbols (.debug.elf file). Uncomment if you wish to use OpenOCD to debug.
 recipe.hooks.objcopy.preobjcopy.1.pattern="{runtime.tools.arduino101load.path}/arduino101load" -c -from="{build.path}/{build.project_name}.elf" -to="{build.path}/../arduino101_sketch.debug.elf"