Hi, thanks @eguiraud…
Unfortunately, the result of a fresh build (git pull and then cmake & make in a new-made directory) of commit 20c1968cf09b6299ad1a46ce5513c37f786a970f (HEAD -> master, origin/master, origin/HEAD) resulted in another “not found”…
[ 45%] Generating G__Core.cxx, ../lib/Core.pcm
/home/furutaka/work/root/root-build-master-20200601/include/module.modulemap:20:42: error: header 'RConfigure.h' not found
module "RConfigure.h" { textual header "RConfigure.h" export * }
^
/home/furutaka/work/root/root-build-master-20200601/include/RtypesCore.h:25:10: note: submodule of top-level module 'ROOT_Config' implicitly imported here
#include "DllImport.h"
^
/home/furutaka/work/root/root-build-master-20200601/include/RtypesCore.h:117:1: error: unknown type name 'R__EXTERN'
R__EXTERN Int_t gDebug;
^
/home/furutaka/work/root/root-build-master-20200601/include/RtypesCore.h:117:16: error: expected ';' after top level declarator
R__EXTERN Int_t gDebug;
^
;
In file included from input_line_5:1:
/home/furutaka/work/root/root-build-master-20200601/include/Rtypes.h:23:10: fatal error: could not build module 'ROOT_Rtypes'
#include "RtypesCore.h"
~~~~~~~~^~~~~~~~~~~~~~
While building module 'Core':
While building module 'ROOT_Foundation_C' imported from /home/furutaka/work/root/root-build-master-20200601/include/Rtypes.h:26:
In file included from <module-includes>:1:
/home/furutaka/work/root/root-build-master-20200601/include/ThreadLocalStorage.h:61:10: fatal error: could not build module 'ROOT_Rtypes'
#include "RtypesCore.h"
~~~~~~~~^~~~~~~~~~~~~~
While building module 'Core':
While building module 'ROOT_Foundation_Stage1_NoRTTI' imported from /home/furutaka/work/root/root-build-master-20200601/include/Rtypes.h:193:
In file included from <module-includes>:5:
/home/furutaka/work/root/root-build-master-20200601/include/TIsAProxy.h:16:10: fatal error: could not build module 'ROOT_Rtypes'
#include "RtypesCore.h"
~~~~~~~~^~~~~~~~~~~~~~
Error: Error loading the default header files.
make[2]: *** [core/CMakeFiles/G__Core.dir/build.make:476: core/G__Core.cxx] Error 1
make[1]: *** [CMakeFiles/Makefile2:17805: core/CMakeFiles/G__Core.dir/all] Error 2
make: *** [Makefile:172: all] Error 2
[furutaka@Furutaka-3 root-build-master-20200601]$ find . -name RtypesCore.h
./include/RtypesCore.h
[furutaka@Furutaka-3 root-build-master-20200601]$ find . -name RConfigure.h
./ginclude/RConfigure.h
Strange… 
Kazuyoshi