Add openlibm to sysimg link line on windows (#53672)

LLVM generates calls to math intrinsics like `trunc` and `rint` (at
least in my local i686 mingw) build, so linking to openlibm is required.
We already have this on the sysimg link line in `Base.link_image`, so
this aligns those options.

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Co-authored-by: Elliot Saba <staticfloat@gmail.com>

sysimage.mk

@@ -17,7 +17,7 @@ $(build_private_libdir)/%.$(SHLIB_EXT): $(build_private_libdir)/%-o.a
 	@$(call PRINT_LINK, $(CXX) $(LDFLAGS) -shared $(fPIC) -L$(build_private_libdir) -L$(build_libdir) -L$(build_shlibdir) -o $@ \
 		$(WHOLE_ARCHIVE) $< $(NO_WHOLE_ARCHIVE) \
 		$(if $(findstring -debug,$(notdir $@)),-ljulia-internal-debug -ljulia-debug,-ljulia-internal -ljulia) \
-		$$([ $(OS) = WINNT ] && echo '' -lssp --disable-auto-import --disable-runtime-pseudo-reloc))
+		$$([ $(OS) = WINNT ] && echo '' $(LIBM) -lssp --disable-auto-import --disable-runtime-pseudo-reloc))
 	@$(INSTALL_NAME_CMD)$(notdir $@) $@
 	@$(DSYMUTIL) $@