gst-build: rtsp-server.h not found

On macOS High Sierra (10.13.6) and Mojave (10.14). With meson (0.49.0) and ninja (1.8.2.post2).

Configuring with meson build finishes successfully and prints this:

Subproject gst-rtsp-server finished.
Message: Created symlink to gst-rtsp-server

Then when executing ninja -C build I get this:

../subprojects/gst-devtools/validate/tools/gst-validate-rtsp-server.c:23:10: fatal error: 'gst/rtsp-server/rtsp-server.h' file not found

More output:

[396/2926] Generating GstBase-1.0.gir with a custom command.
FAILED: subprojects/gst-devtools/validate/tools/ee26439@@gst-validate-rtsp-server-1.0@exe/gst-validate-rtsp-server.c.o
cc 
-Isubprojects/gst-devtools/validate/tools/ee26439@@gst-validate-rtsp-server-1.0@exe 
-Isubprojects/gst-devtools/validate/tools 
-I../subprojects/gst-devtools/validate/tools 
-Isubprojects/gst-devtools/validate 
-I../subprojects/gst-devtools/validate 
-Isubprojects/gstreamer 
-I../subprojects/gstreamer 
-Isubprojects/gstreamer/gst 
-I/usr/local/include/gstreamer-1.0 
-I/usr/local/Cellar/glib/2.58.2/include/glib-2.0 
-I/usr/local/Cellar/glib/2.58.2/lib/glib-2.0/include 
-I/usr/local/opt/gettext/include 
-I/usr/local/Cellar/pcre/8.42/include -Xclang -fcolor-diagnostics -pipe -Wall -Winvalid-pch -O2 -g -fvisibility=hidden -fno-strict-aliasing -Wmissing-declarations -Wmissing-prototypes -Wredundant-decls -Wundef -Wwrite-strings -Wformat -Wformat-nonliteral -Wformat-security -Winit-self -Wmissing-include-dirs -Waddress -Wno-multichar -Wdeclaration-after-statement -Wvla -Wpointer-arith -D_REENTRANT -DHAVE_CONFIG_H -DGST_USE_UNSTABLE_API  -MD -MQ 
'subprojects/gst-devtools/validate/tools/ee26439@@gst-validate-rtsp-server-1.0@exe/gst-validate-rtsp-server.c.o' -MF 
'subprojects/gst-devtools/validate/tools/ee26439@@gst-validate-rtsp-server-1.0@exe/gst-validate-rtsp-server.c.o.d' -o 
'subprojects/gst-devtools/validate/tools/ee26439@@gst-validate-rtsp-server-1.0@exe/gst-validate-rtsp-server.c.o' -c ../subprojects/gst-devtools/validate/tools/gst-validate-rtsp-server.c