Revert "[flang] Fix a warning"

This reverts commit 18734f60.

This caused a test suite failure on our bots:
https://lab.llvm.org/buildbot/#/builders/184/builds/9407

```
$ ~/stage1.install/bin/flang-new flush_1.f90
/usr/bin/ld: /home/david.spickett/stage1.install/lib/libFortranRuntime.a(extensions.cpp.o): in function `getlog_':
extensions.cpp:(.text.getlog_+0x1c): undefined reference to `operator new(unsigned long)'
/usr/bin/ld: extensions.cpp:(.text.getlog_+0x7c): undefined reference to `operator delete(void*)'
/usr/bin/ld: extensions.cpp:(.text.getlog_+0xc4): undefined reference to `operator delete(void*)'
/usr/bin/ld: extensions.cpp:(.text.getlog_+0xe8): undefined reference to `operator delete(void*)'
flang-new: error: linker command failed with exit code 1 (use -v to see invocation)
```