It was a bug, easily fixed by removing a single dollar sign:
index 2480267..338016c 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -384,7 +384,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
dnl qt version is set to 'auto' and the preferred version wasn't found. Now try the other.
if test x$have_qt = xno && test x$bitcoin_qt_want_version = xauto; then
- if test x$auto_priority_version = x$qt5; then
+ if test x$auto_priority_version = xqt5; then
PKG_CHECK_MODULES([QT], [$qt4_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes; QT_LIB_PREFIX=Qt; bitcoin_qt_got_major_vers=4], [have_qt=no])
else
PKG_CHECK_MODULES([QT], [$qt5_modules], [QT_INCLUDES="$QT_CFLAGS"; have_qt=yes; QT_LIB_PREFIX=Qt5; bitcoin_qt_got_major_vers=5], [have_qt=no])
Do you know if that is fixed in master?
EDIT - doesn't look like it. Is there a bug report or a PR to fix it?
I don't need it fixed anymore but it probably should be fixed.
EDIT2 - https://github.com/bitcoin/bitcoin/pull/7604 is it.