dev-cpp/xtl: avoid unnecessary test compilation during src_install

Signed-off-by: Kamal Abdellatif <gentoo.kamal@tgf.pw>

dev-cpp/xtl/xtl-0.7.5.ebuild

@@ -3,6 +3,9 @@
 
 EAPI=8
 
+# required because of manual install in src_install
+CMAKE_MAKEFILE_GENERATOR="emake"
+
 PYTHON_COMPAT=( python3_{9..11} )
 
 inherit cmake python-any-r1
@@ -57,3 +60,11 @@ src_compile() {
 src_test() {
 	cmake_src_compile xtest
 }
+
+src_install() {
+	# Default install target depends on tests with USE=test enabled.
+	# However, this is a header-only library.
+	DESTDIR="${D}" cmake_build install/fast "$@"
+
+	einstalldocs
+}