depends: Delay expansion of per-package vars

Prior to this commit, when int_vars was called for packages, it would
immediately expand the "single-dollar variables", which may be defined
in terms of variables which are not yet determined (e.g. variables
defined in package/*.mk, which are included after int_vars is called).

This is required for the next commit as after that commit, for darwin
cross-builds:

0. int_vars is defined in terms of $(1)_cc
1. $(1)_cc is defined in terms of darwin_CC
2. ... which is defined in terms of clang_resource_dir
3. ... which is defined in terms of native_cctools_clang_version
4. which is undetermined at the time when int_vars is being expanded and evaluated

depends/funcs.mk

@@ -1,17 +1,23 @@
 define int_vars
 #Set defaults for vars which may be overridden per-package
-$(1)_cc=$($($(1)_type)_CC)
-$(1)_cxx=$($($(1)_type)_CXX)
-$(1)_objc=$($($(1)_type)_OBJC)
-$(1)_objcxx=$($($(1)_type)_OBJCXX)
-$(1)_ar=$($($(1)_type)_AR)
-$(1)_ranlib=$($($(1)_type)_RANLIB)
-$(1)_libtool=$($($(1)_type)_LIBTOOL)
-$(1)_nm=$($($(1)_type)_NM)
-$(1)_cflags=$($($(1)_type)_CFLAGS) $($($(1)_type)_$(release_type)_CFLAGS)
-$(1)_cxxflags=$($($(1)_type)_CXXFLAGS) $($($(1)_type)_$(release_type)_CXXFLAGS)
-$(1)_ldflags=$($($(1)_type)_LDFLAGS) $($($(1)_type)_$(release_type)_LDFLAGS) -L$($($(1)_type)_prefix)/lib
-$(1)_cppflags=$($($(1)_type)_CPPFLAGS) $($($(1)_type)_$(release_type)_CPPFLAGS) -I$($($(1)_type)_prefix)/include
+$(1)_cc=$$($$($(1)_type)_CC)
+$(1)_cxx=$$($$($(1)_type)_CXX)
+$(1)_objc=$$($$($(1)_type)_OBJC)
+$(1)_objcxx=$$($$($(1)_type)_OBJCXX)
+$(1)_ar=$$($$($(1)_type)_AR)
+$(1)_ranlib=$$($$($(1)_type)_RANLIB)
+$(1)_libtool=$$($$($(1)_type)_LIBTOOL)
+$(1)_nm=$$($$($(1)_type)_NM)
+$(1)_cflags=$$($$($(1)_type)_CFLAGS) \
+            $$($$($(1)_type)_$$(release_type)_CFLAGS)
+$(1)_cxxflags=$$($$($(1)_type)_CXXFLAGS) \
+              $$($$($(1)_type)_$$(release_type)_CXXFLAGS)
+$(1)_ldflags=$$($$($(1)_type)_LDFLAGS) \
+             $$($$($(1)_type)_$$(release_type)_LDFLAGS) \
+             -L$$($($(1)_type)_prefix)/lib
+$(1)_cppflags=$$($$($(1)_type)_CPPFLAGS) \
+              $$($$($(1)_type)_$$(release_type)_CPPFLAGS) \
+              -I$$($$($(1)_type)_prefix)/include
 $(1)_recipe_hash:=
 endef