qt5-build.eclass: Symlink necessary tools to /usr/bin

According to upstream discussion on Qt6 recommended tools to be in PATH.
See also: https://lists.qt-project.org/pipermail/development/2020-November/040626.html

With '5' suffix:
- qmake
- qml
- qtdiag
- qtpaths
- designer

Without suffix:
- assistant
- qdbus
- qdbusviewer
- linguist

Signed-off-by: Andreas Sturmlechner <asturm@gentoo.org>

eclass/qt5-build.eclass

@@ -279,6 +279,20 @@ qt5-build_src_install() {
 
 	qt5_install_module_config
 
+	if ver_test ${PV} -ge 5.15.2; then
+		case ${PN} in
+			qtcore) qt5_symlink_binary_to_path qmake 5 ;;
+			qtdeclarative) qt5_symlink_binary_to_path qml 5 ;;
+			qtdiag) qt5_symlink_binary_to_path qtdiag 5 ;;
+			qtpaths) qt5_symlink_binary_to_path qtpaths 5 ;;
+			designer) qt5_symlink_binary_to_path designer 5 ;;
+			assistant) qt5_symlink_binary_to_path assistant ;;
+			qdbus) qt5_symlink_binary_to_path qdbus ;;
+			qdbusviewer) qt5_symlink_binary_to_path qdbusviewer ;;
+			linguist) qt5_symlink_binary_to_path linguist ;;
+		esac
+	fi
+
 	# prune libtool files
 	find "${D}" -name '*.la' -type f -delete || die
 }
@@ -469,6 +483,15 @@ qt5_symlink_tools_to_build_dir() {
 	popd >/dev/null || die
 }
 
+# @FUNCTION: qt5_symlink_binary_to_path
+# @USAGE: <target binary name> [suffix]
+# @INTERNAL
+# @DESCRIPTION:
+# Symlink a given binary from QT5_BINDIR to QT5_PREFIX/bin, with optional suffix
+qt5_symlink_binary_to_path() {
+	dosym ../../"${QT5_BINDIR#${EPREFIX}/}"/${1} /usr/bin/${1}${2}
+}
+
 # @FUNCTION: qt5_base_configure
 # @INTERNAL
 # @DESCRIPTION: