title: Cmake compile error when include cmath header
body: <p>Here is my code:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;cmath&gt;
  
  int main() {
      std::cout &lt;&lt; std::sqrt(4) &lt;&lt; std::endl;
      return 0;
  }
  </code></pre>
  
  <p>MAC OS 10.15, CMake 3.15.4</p>
  
  <p>As long as the header file cmath.h is included, CMake compile error. </p>
  
  <p>Execute command:</p>
  
  <pre><code>cmake --build /Users/xxx/Documents/Playground/test1/cmake-build-debug --target test1 -- -j 4
  </code></pre>
  
  <p>Got following errors:</p>
  
  <pre><code>/Applications/CLion.app/Contents/bin/cmake/mac/bin/cmake --build /Users/xxx/Documents/Playground/test/cmake-build-debug --target test -- -j 4
  Scanning dependencies of target test
  [ 50%] Building CXX object CMakeFiles/test.dir/main.cpp.o
  In file included from /Users/xxx/Documents/Playground/test/main.cpp:2:
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:314:9: error: no member named 'signbit' in the global namespace
  using ::signbit;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:315:9: error: no member named 'fpclassify' in the global namespace
  using ::fpclassify;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:316:9: error: no member named 'isfinite' in the global namespace; did you mean 'finite'?
  using ::isfinite;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/math.h:749:12: note: 'finite' declared here
  extern int finite(double)
  ^
  In file included from /Users/xxx/Documents/Playground/test/main.cpp:2:
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:317:9: error: no member named 'isinf' in the global namespace
  using ::isinf;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:318:9: error: no member named 'isnan' in the global namespace
  using ::isnan;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:319:9: error: no member named 'isnormal' in the global namespace
  using ::isnormal;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:320:7: error: no member named 'isgreater' in the global namespace; did you mean '::std::greater'?
  using ::isgreater;
  ^~
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/functional:728:29: note: '::std::greater' declared here
  struct _LIBCPP_TEMPLATE_VIS greater : binary_function&lt;_Tp, _Tp, bool&gt;
  ^
  In file included from /Users/xxx/Documents/Playground/test/main.cpp:2:
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:321:7: error: no member named 'isgreaterequal' in the global namespace; did you mean '::std::greater_equal'?
  using ::isgreaterequal;
  ^~
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/functional:757:29: note: '::std::greater_equal' declared here
  struct _LIBCPP_TEMPLATE_VIS greater_equal : binary_function&lt;_Tp, _Tp, bool&gt;
  ^
  In file included from /Users/xxx/Documents/Playground/test/main.cpp:2:
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:322:9: error: no member named 'isless' in the global namespace
  using ::isless;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:323:9: error: no member named 'islessequal' in the global namespace
  using ::islessequal;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:324:9: error: no member named 'islessgreater' in the global namespace
  using ::islessgreater;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:325:9: error: no member named 'isunordered' in the global namespace
  using ::isunordered;
  ~~^
  /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/cmath:326:9: error: no member named 'isunordered' in the global namespace
  using ::isunordered;
  ~~^
  13 errors generated.
  gmake[3]: *** [CMakeFiles/test.dir/build.make:63: CMakeFiles/test.dir/main.cpp.o] Error 1
  gmake[2]: *** [CMakeFiles/Makefile2:76: CMakeFiles/test.dir/all] Error 2
  gmake[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/test.dir/rule] Error 2
  gmake: *** [Makefile:118: test] Error 2
  </code></pre>
  
  <p>Same code compiled successfully with XCode.
  CMake works fine if remove the include of header file cmath. However I need to use functions in cmath and that cannot be workaround.</p>