Reland "git-2.eclass: Use BDEPEND if available"

This is a reland of 36a998a520ed633eb3586e67e4fa126bd9689b9a
Having git in BDEPEND should be alright now that build_packages has been
changed to `rebuild-if-new-rev` rather than `rebuild-if-unbuilt`. That
change should avoid triggering the bug that caused Perl packages to be
installed to board targets.

Original change's description:
> git-2.eclass: Use BDEPEND if available
>
> TEST=None
> BUG=chromium:1011992
>
> Change-Id: Ia2580c5b48677def61f34bc2a913e38acc534b47
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/1845661
> Tested-by: Chris McDonald <cjmcdonald@chromium.org>
> Auto-Submit: Chris McDonald <cjmcdonald@chromium.org>
> Reviewed-by: Mike Frysinger <vapier@chromium.org>
> Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>

Bug: chromium:1011992
Change-Id: I475b2f89df448264af258db5cd635d54ae044921
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/1872183
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/eclass/git-2.eclass b/eclass/git-2.eclass
index fdc2f18..a099c08 100644
--- a/eclass/git-2.eclass
+++ b/eclass/git-2.eclass
@@ -14,7 +14,11 @@
 # This eclass support all EAPIs.
 EXPORT_FUNCTIONS src_unpack
 
-DEPEND="dev-vcs/git"
+if [[ ${EAPI:-0} != [0123456] ]]; then
+	BDEPEND="dev-vcs/git"
+else
+	DEPEND="dev-vcs/git"
+fi
 
 # @ECLASS-VARIABLE: EGIT_SOURCEDIR
 # @DESCRIPTION: