app-crypt/sequoia-sq: use llvm.eclass for bindgen

Just like 1fd5803705. Could bump the crates
like gyakovlev said but we're about to do that for a bump anyway.

Closes: https://bugs.gentoo.org/894358
Signed-off-by: Sam James <sam@gentoo.org>

app-crypt/sequoia-sq/sequoia-sq-0.28.0.ebuild

@@ -419,7 +419,10 @@ CRATES="
 	zeroize_derive-1.3.2
 "
 
-inherit bash-completion-r1 cargo
+# TODO: Should be able to try 16 in next release after 0.28.0
+LLVM_MAX_SLOT=15
+
+inherit bash-completion-r1 cargo llvm
 
 DESCRIPTION="CLI of the Sequoia OpenPGP implementation"
 HOMEPAGE="https://sequoia-pgp.org/ https://gitlab.com/sequoia-pgp/sequoia"
@@ -448,10 +451,16 @@ DEPEND="
 	${COMMON_DEPEND}
 "
 RDEPEND="${COMMON_DEPEND}"
+# Clang needed for bindgen
 BDEPEND="
+	<sys-devel/clang-$((${LLVM_MAX_SLOT} + 1))
 	virtual/pkgconfig
 "
 
+llvm_check_deps() {
+	has_version -b "sys-devel/clang:${LLVM_SLOT}"
+}
+
 src_compile() {
 	cd sq || die
 	# Setting CARGO_TARGET_DIR is required to have the build system