[flang][nfc] Avoid generating external-hello-world by default

[sunshaoce]

Summary

The current setting is not working.
When compiling flang, the external-hello-world is still compiled by default.

[luporl]

Looks good to me.

flang/examples/CMakeLists.txt

2

This doesn't seem to be needed.

[sunshaoce]

Address @luporl's comment

flang/examples/CMakeLists.txt

 if(NOT FLANG_BUILD_EXAMPLES)
-  set(EXCLUDE_FROM_ALL ON)
+  set_property(DIRECTORY PROPERTY EXCLUDE_FROM_ALL ON)
 endif()
 
-# This test is not run by default as it requires input.
-add_executable(external-hello-world
-  external-hello.cpp
-)
-
-target_link_libraries(external-hello-world
-  FortranRuntime
-)
-
+add_subdirectory(ExternalHelloWorld)
 add_subdirectory(PrintFlangFunctionNames)
 add_subdirectory(FlangOmpReport)

flang/examples/ExternalHelloWorld/CMakeLists.txt

-if(NOT FLANG_BUILD_EXAMPLES)
-  set(EXCLUDE_FROM_ALL ON)
-endif()
-
 # This test is not run by default as it requires input.
 add_executable(external-hello-world
   external-hello.cpp
 )
 
 target_link_libraries(external-hello-world
   FortranRuntime
 )
-
-add_subdirectory(PrintFlangFunctionNames)
-add_subdirectory(FlangOmpReport)

flang/examples/ExternalHelloWorld/external-hello.cpp

 #include "flang/Runtime/io-api.h"
 #include "flang/Runtime/main.h"
 #include "flang/Runtime/stop.h"
 #include <cstring>
 #include <limits>
 
 using namespace Fortran::runtime::io;
 
 void output1() {
   auto io{IONAME(BeginExternalListOutput)()};
   const char str[]{"Hello, world!"};
   IONAME(OutputAscii)(io, str, std::strlen(str));
   IONAME(OutputInteger64)(io, 678);
   IONAME(OutputReal64)(io, 0.0);
   IONAME(OutputReal64)(io, 2.0 / 3.0);
   IONAME(OutputReal64)(io, 1.0e99);
   IONAME(OutputReal64)(io, std::numeric_limits<double>::infinity());
   IONAME(OutputReal64)(io, -std::numeric_limits<double>::infinity());
   IONAME(OutputReal64)(io, std::numeric_limits<double>::quiet_NaN());
   IONAME(OutputComplex64)(io, 123.0, -234.0);
   IONAME(OutputLogical)(io, false);
   IONAME(OutputLogical)(io, true);
   IONAME(EndIoStatement)(io);
 }
 
 void input1() {
   auto io{IONAME(BeginExternalListOutput)()};
   const char prompt[]{"Enter an integer value:"};
   IONAME(OutputAscii)(io, prompt, std::strlen(prompt));
   IONAME(EndIoStatement)(io);
 
   io = IONAME(BeginExternalListInput)();
   std::int64_t n{-666};
   IONAME(InputInteger)(io, n);
   IONAME(EndIoStatement)(io);
 
   io = IONAME(BeginExternalListOutput)();
   const char str[]{"Result:"};
   IONAME(OutputAscii)(io, str, std::strlen(str));
   IONAME(OutputInteger64)(io, n);
   IONAME(EndIoStatement)(io);
 }
 
 int main(int argc, const char *argv[], const char *envp[]) {
   RTNAME(ProgramStart)(argc, argv, envp, nullptr);
   output1();
   input1();
   RTNAME(PauseStatement)();
   RTNAME(ProgramEndStatement)();
   return 0;
 }