build from scratch worked, rebuild failed

F:\Tmp\qbs-bug>qbs resolve profile:qt5x64 -f root.qbs project.targetProj:all
Build graph does not yet exist for configuration 'default'. Starting from scratch.
Resolving project for configuration default
Setting up Qt at 'c:\Lib\Qt\5.9.7.static_x64\bin\qmake.exe'...
Qt was set up successfully.
Setting up build graph for configuration default

F:\Tmp\qbs-bug>qbs build profile:qt5x64 -f root.qbs project.targetProj:all
Restoring build graph from disk
Building for configuration default
compiling src4.cpp [lib4]
Creating static import for plugin 'qjpeg'. [app1]
Creating static import for plugin 'qicns'. [app1]
Creating static import for plugin 'qtga'. [app1]
Creating static import for plugin 'qwbmp'. [app1]
Creating static import for plugin 'qwebp'. [app1]
Creating static import for plugin 'qico'. [app1]
Creating static import for plugin 'qgif'. [app1]
Creating static import for plugin 'qtiff'. [app1]
Creating static import for plugin 'qwindows'. [app1]
uic m1.ui [app1]
Creating static import for plugin 'qwbmp'. [app2]
Creating static import for plugin 'qtiff'. [app2]
Creating static import for plugin 'qjpeg'. [app2]
Creating static import for plugin 'qtga'. [app2]
Creating static import for plugin 'qico'. [app2]
Creating static import for plugin 'qwebp'. [app2]
Creating static import for plugin 'qwindows'. [app2]
Creating static import for plugin 'qicns'. [app2]
uic m2.ui [app2]
Creating static import for plugin 'qgif'. [app2]
moc m2.h [app2]
moc m1.h [app1]
compiling app2_qt_plugin_import_qtga.cpp [app2]
compiling app2_qt_plugin_import_qwbmp.cpp [app2]
compiling app2_qt_plugin_import_qwindows.cpp [app2]
compiling app2_qt_plugin_import_qico.cpp [app2]
compiling app2_qt_plugin_import_qicns.cpp [app2]
compiling app2_qt_plugin_import_qwebp.cpp [app2]
compiling m2.cpp [app2]
compiling app2_qt_plugin_import_qjpeg.cpp [app2]
compiling app2_qt_plugin_import_qtiff.cpp [app2]
compiling moc_m2.cpp [app2]
compiling app1_qt_plugin_import_qwbmp.cpp [app1]
creating lib4.lib [lib4]
compiling app1_qt_plugin_import_qtga.cpp [app1]
compiling m1.cpp [app1]
compiling app1_qt_plugin_import_qico.cpp [app1]
compiling app1_qt_plugin_import_qjpeg.cpp [app1]
compiling app1_qt_plugin_import_qgif.cpp [app1]
compiling app1_qt_plugin_import_qwebp.cpp [app1]
compiling moc_m1.cpp [app1]
compiling app1_qt_plugin_import_qicns.cpp [app1]
compiling app1_qt_plugin_import_qtiff.cpp [app1]
compiling app1_qt_plugin_import_qwindows.cpp [app1]
compiling app2_qt_plugin_import_qgif.cpp [app2]
linking app2.exe [app2]
linking app1.exe [app1]
Build done for configuration default.

F:\Tmp\qbs-bug>qbs resolve profile:qt5x64 -f root.qbs
Restoring build graph from disk
Resolving project for configuration default

F:\Tmp\qbs-bug>qbs build profile:qt5x64 -f root.qbs -p all-libs
Restoring build graph from disk
Building for configuration default
compiling src4.cpp [lib4]
creating lib4.lib [lib4]
Build done for configuration default.

F:\Tmp\qbs-bug>qbs resolve profile:qt5x64 -f root.qbs project.targetProj:all
Restoring build graph from disk

F:\Tmp\qbs-bug>qbs build profile:qt5x64 -f root.qbs project.targetProj:all
 Restoring build graph from disk
 Building for configuration default
 linking app2.exe [app2]
 linking app1.exe [app1]
... skipped command-line echo ...
LINK : fatal error LNK1104: cannot open file 'F:\Tmp\qbs-bug\default\app2.998ffe0d\3a52ce780950d4d9\app2_qt_plugin_import_qgif.cpp.obj'
LINK : fatal error LNK1104: cannot open file 'F:\Tmp\qbs-bug\default\app1.171ee6b1\3a52ce780950d4d9\app1_qt_plugin_import_qgif.cpp.obj'