Xcode project generator expands location macros in linker flags

Created by: ProfessaA

background

Previously, ProjectGenerator did not expand location macros used in linker flags. As a result, buck builds for targets with linker flags using location macros would succeed but building a project generated from the same target would fail.

change

ProjectGenerator now expands location macros to their absolute path and adds the macro's build target to the ProjectGenerator's list of required targets.

verification

• add ProjectGeneratorTest.testAppleLibraryLinkerFlagsWithLocationMacrosAreExpanded
• buck test test/com/facebook/buck/apple/project_generator:project_generator
• verify that buck project generates a project with linker flag location macros correctly expanded, and that the targets of those macros were built as part of project generation