Build failure on macOS 10.15

[jmkuhn]

After #49740. @vtjnash

...
    CC src/ircode.o
    CC src/opaque_closure.o
    CC src/codegen-stubs.o
    CC src/coverage.o
    CC src/runtime_ccall.o
    LINK usr/lib/libjulia-internal.1.10.dylib
Undefined symbols for architecture x86_64:
  "__dyld_dlopen_atfork_parent", referenced from:
      _mach_profile_listener in signal-handling.o
      _signal_listener in signal-handling.o
  "__dyld_dlopen_atfork_prepare", referenced from:
      _mach_profile_listener in signal-handling.o
      _signal_listener in signal-handling.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[1]: *** [/opt/julia/1.10-DEV/julia/usr/lib/libjulia-internal.1.10.dylib] Error 1
make: *** [julia-src-release] Error 2
% sw_vers 
ProductName:	Mac OS X
ProductVersion:	10.15.7
BuildVersion:	19H2026
% pkgutil --pkg-info=com.apple.pkg.CLTools_Executables
package-id: com.apple.pkg.CLTools_Executables
version: 12.4.0.0.1.1610135815
volume: /
location: /
install-time: 1683830967
groups: com.apple.FindSystemFiles.pkg-group