pkg-generic.mk: strip leading/trailing spaces

The manual gives this example for using the github macro:

  FOO_VERSION = v1.0 # tag or full commit ID

Unfortunately, people copy/pasting this example will face weird make errors,
because it leads the FOO_VERSION variable to end with a space.  Similar
problems can happen when testing a version bump or similar, so strip
leading/trailing spaces before the version is used to construct the build
directory path.

Reported-by: Edd Robbins <edd.robbins@gmail.com>
Cc: Edd Robbins <edd.robbins@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pkg-generic.mk

@@ -318,15 +318,15 @@ $(2)_RAWNAME			=  $$(patsubst host-%,%,$(1))
 # version control system branch or tag, for example remotes/origin/1_10_stable.
 ifndef $(2)_VERSION
  ifdef $(3)_VERSION
-  $(2)_DL_VERSION := $$($(3)_VERSION)
-  $(2)_VERSION := $$(subst /,_,$$($(3)_VERSION))
+  $(2)_DL_VERSION := $$(strip $$($(3)_VERSION))
+  $(2)_VERSION := $$(subst /,_,$$(strip $$($(3)_VERSION)))
  else
   $(2)_VERSION = undefined
   $(2)_DL_VERSION = undefined
  endif
 else
-  $(2)_DL_VERSION := $$($(2)_VERSION)
-  $(2)_VERSION := $$(subst /,_,$$($(2)_VERSION))
+  $(2)_DL_VERSION := $$(strip $$($(2)_VERSION))
+  $(2)_VERSION := $$(strip $$(subst /,_,$$($(2)_VERSION)))
 endif
 
 $(2)_BASE_NAME	=  $(1)-$$($(2)_VERSION)