build: Don't regenerate node symlink

The node -> out/*/node symlink is getting recreated in parallel with other targets in the makefile which require it (e.g. test-ci) and this seems to be causing a race condition which is showing up on AIX Ref: #9825

Author: sxa555

Makefile

@@ -64,13 +64,18 @@ endif
 # to check for changes.
 .PHONY: $(NODE_EXE)$(NODE_G_EXE)
 
+# The -r/-L check stops it recreating the link if it is already in place,
+# otherwise $(NODE_EXE) being a .PHONY target means it is always re-run. 
+# Without the check there is a race condition between the link being deleted
+# and recreated which can break the addons build when running test-ci
+# See comments on the build-addons target for some more info
 $(NODE_EXE): config.gypi out/Makefile
 $(MAKE) -C out BUILDTYPE=Release V=$(V)
- ln -fs out/Release/$(NODE_EXE)$@
+if [ !-r$(NODE_EXE)-o!-L$(NODE_EXE) ];thenln -fs out/Release/$(NODE_EXE)$@;fi
 
 $(NODE_G_EXE): config.gypi out/Makefile
 $(MAKE) -C out BUILDTYPE=Debug V=$(V)
- ln -fs out/Debug/$(NODE_EXE)$@
+if [ !-r$(NODE_EXE)-o!-L$(node_EXE) ];thenln -fs out/Debug/$(NODE_EXE)$@;fi
 
 out/Makefile: common.gypi deps/uv/uv.gyp deps/http_parser/http_parser.gyp \
  deps/zlib/zlib.gyp deps/v8/gypfiles/toolchain.gypi \