[CMake][compiler-rt] Use COMPILE_OPTIONS and LINK_OPTIONS

[phosek]

Summary

This avoids the need for string-ification and lets CMake deduplicate
potentially duplicate flags.

[smeenai]

One issue I've had in the past is that CMake "helpfully" deduplicates flags specified via target_compile_options (and I assume that'll happen for setting the COMPILE_OPTIONS property as well), which turns things like -isystem /foo -isystem /bar into -isystem /foo /bar and breaks things. Is that a risk here? See https://gitlab.kitware.com/cmake/cmake/-/issues/15826

[phosek]

In D122750#3417264, @smeenai wrote:

One issue I've had in the past is that CMake "helpfully" deduplicates flags specified via target_compile_options (and I assume that'll happen for setting the COMPILE_OPTIONS property as well), which turns things like -isystem /foo -isystem /bar into -isystem /foo /bar and breaks things. Is that a risk here? See https://gitlab.kitware.com/cmake/cmake/-/issues/15826

I haven't encountered any issues in my testing. The problem with COMPILE_FLAGS and LINK_FLAGS is that these don't seem to expand generator expressions while COMPILE_OPTIONS and LINK_OPTIONS do. I have a follow up change that revamps the use libc++ headers from compiler-rt and relies on generator expressions so this is a prerequisite.

[smeenai]

In D122750#3418560, @phosek wrote:

In D122750#3417264, @smeenai wrote:

One issue I've had in the past is that CMake "helpfully" deduplicates flags specified via target_compile_options (and I assume that'll happen for setting the COMPILE_OPTIONS property as well), which turns things like -isystem /foo -isystem /bar into -isystem /foo /bar and breaks things. Is that a risk here? See https://gitlab.kitware.com/cmake/cmake/-/issues/15826

I haven't encountered any issues in my testing. The problem with COMPILE_FLAGS and LINK_FLAGS is that these don't seem to expand generator expressions while COMPILE_OPTIONS and LINK_OPTIONS do. I have a follow up change that revamps the use libc++ headers from compiler-rt and relies on generator expressions so this is a prerequisite.

SGTM

compiler-rt/cmake/Modules/CompilerRTUtils.cmake

 include(CMakePushCheckState)
 include(CheckSymbolExists)
 
 # Because compiler-rt spends a lot of time setting up custom compile flags,
 # define a handy helper function for it. The compile flags setting in CMake
 # has serious issues that make its syntax challenging at best.
 function(set_target_compile_flags target)
-  set(argstring "")
-  foreach(arg ${ARGN})
-    set(argstring "${argstring} ${arg}")
-  endforeach()
-  set_property(TARGET ${target} PROPERTY COMPILE_FLAGS "${argstring}")
+  set_property(TARGET ${target} PROPERTY COMPILE_OPTIONS ${ARGN})
 endfunction()
 
 function(set_target_link_flags target)
-  set(argstring "")
-  foreach(arg ${ARGN})
-    set(argstring "${argstring} ${arg}")
-  endforeach()
-  set_property(TARGET ${target} PROPERTY LINK_FLAGS "${argstring}")
+  set_property(TARGET ${target} PROPERTY LINK_OPTIONS ${ARGN})
 endfunction()
 
 # Set the variable var_PYBOOL to True if var holds a true-ish string,
 # otherwise set it to False.
 macro(pythonize_bool var)
   if (${var})
     set(${var}_PYBOOL True)
   else()