nettle: Respect portage host cc variable

Pass CC_FOR_BUILD to econf. Otherwise it invokes gcc instead of portage
specified HOST/BUILD CC.

Gentoo PR: https://github.com/gentoo/gentoo/pull/16156

BUG=chromium:979916, chromium:991812, chromium:1088242
TEST=CQ

Change-Id: I8cc38fb3cb8094d5e9ef0aad35e3755b7ab1e09d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2240124
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
diff --git a/dev-libs/nettle/nettle-3.4.1.ebuild b/dev-libs/nettle/nettle-3.4.1-r1.ebuild
similarity index 97%
rename from dev-libs/nettle/nettle-3.4.1.ebuild
rename to dev-libs/nettle/nettle-3.4.1-r1.ebuild
index 53ab985..f557ceb 100644
--- a/dev-libs/nettle/nettle-3.4.1.ebuild
+++ b/dev-libs/nettle/nettle-3.4.1-r1.ebuild
@@ -50,6 +50,7 @@
 multilib_src_configure() {
 	# --disable-openssl bug #427526
 	ECONF_SOURCE="${S}" econf \
+		CC_FOR_BUILD="$(tc-getBUILD_CC)" \
 		--libdir="${EPREFIX}"/usr/$(get_libdir) \
 		--disable-openssl \
 		--disable-fat \