Why does qmake not correctly process rm files during rebuild using a special compiler?

Question

I am trying to get trift framework samples to build in Qt qmake and I see a problem when I rebuild my project. My question is:

• What am I doing wrong that causes the makefile to concatenate all .out files along with spaces in the rm call? ''

First, I will show the output, and then go into the specification.

Error: - see the first command "rm" rm -fthrifttest .... ( does each file name run together? Why?)

06:09:37: Running steps for project thrifttest...
06:09:37: Starting: "/usr/bin/make" clean
/opt/Qt/5.4/gcc/bin/qmake -spec linux-g++ CONFIG+=debug -o Makefile ../../thrifttest/idl/idl.pro
rm -fthrifttest/idl/tutorial.outthrifttest/idl/shared.out
rm -f Calculator.o shared_constants.o shared_types.o SharedService.o tutorial_constants.o tutorial_types.o
rm -f *~ core *.core
rm: invalid option -- 't'
Try 'rm --help' for more information.
make: [compiler_idl_clean] Error 1 (ignored)
06:09:37: The process "/usr/bin/make" exited normally.
06:09:37: Starting: "/opt/Qt/5.4/gcc/bin/qmake" /home/developer/dev/thrifttest/idl/idl.pro -r -spec linux-g++ CONFIG+=debug
06:09:37: The process "/opt/Qt/5.4/gcc/bin/qmake" exited normally.
06:09:37: Starting: "/usr/bin/make" 
g++ -c -pipe -g -Wall -W -D_REENTRANT -fPIC  -I../../thrifttest/idl -I. -I/opt/Qt/5.4/gcc/mkspecs/linux-g++ -o Calculator.o ../../thrifttest/idl/gen-cpp/Calculator.cpp
.... 
etc.

.pro file design - Qt version 5.4

QT        -= core
QT        -= gui
TEMPLATE  = lib

# the IDL files I am interested in.
THRIFTSOURCES = \
    tutorial.thrift \
    shared.thrift

#----------------------------------------------------------------------------------------
# a special tool (compiler) that generates the appropriate .cpp and .h files from the IDL generator
# called 'thrift'. There is a ton of undocumented nuggets in here
#
#  IN_PWD — the base directory of the source tree
#  QMAKE_FILE_BASE - the current processing filename without extension or path. Changes for each call to .commands
#  QMAKE_FILE_IN - the current processing filename including its path and extension. Changes for each call to .commands
#  $$escape_expand(\\n\\t) - a way to output more than one command (could have added '&&' as well)
#
#  idl.output -  sets the output file name that the step will generate. In this case I am creating
#                a touched .out file to match against the .thrift file processed. This file is matched by
#                timestamp against the current input file to determine if it needs building.
#  idl.input - The tool will iterate through the specified files.
#  idl.commands - this is the guts of the compiler tool. The commands listed here act upon files found
#                 in the .input list that need to be updated.
#  idl.name - this appears to just be an internal name used in qmake;
#             just ensure you use a different value for each custom compiler.
#  idl.variable_out - the generated target files outputted from the build step will be added to this variable
#  idl.CONFIG - target_predeps — I *think* this makes sure that the custom compiler
#                                is run as the first thing in the project...
#               no_link -  the files that are created should not be added to OBJECTS —
#                          i.e., they are not compiled code which should be linked
#----------------------------------------------------------------------------------------

idl.output   = $${IN_PWD}/${QMAKE_FILE_BASE}.out
idl.input    = THRIFTSOURCES
idl.commands = thrift -r -o "$${IN_PWD}" --gen cpp ${QMAKE_FILE_IN}$$escape_expand(\\n\\t) \
               touch $${IN_PWD}/${QMAKE_FILE_BASE}.out$$escape_expand(\\n\\t)
idl.name     = thrift-compiler 
idl.variable_out = JUNK
idl.CONFIG = no_link target_predeps # guarantee this is called before the regular compiler actions.
QMAKE_EXTRA_COMPILERS += idl        # add to the compiler action list.

#----------------------------------------------------------------------------------------
# We have no idea how many .cpp files will be generated by the IDL compiler. This
# set of lines finds all the .cpp files and then eliminates all the *.skeleton.cpp files
# (which are just sample applications and not needed by our library code).
# Once a good list is defined, then make it the SOURCES list to use as the build
# structure. The $$files(glob) is an UNDOCUMENTED function to handle wildcard searches.
# Hack. Hack. Hack.
#----------------------------------------------------------------------------------------
TESTS = $$files($${IN_PWD}/gen-cpp/*.cpp)
SKELS = $$files($${IN_PWD}/gen-cpp/*.skeleton.cpp)
TESTS -= $$SKELS

HEADERS = $$files($${IN_PWD}/gen-cpp/*.h)
SOURCES = $$TESTS

Directory structure of source files

├── idl
│   ├── gen-cpp  <--- generated files go in here
│   │   ├── Calculator.cpp
│   │   ├── Calculator.h
│   │   ├── Calculator_server.skeleton.cpp
│   │   ├── shared_constants.cpp
│   │   ├── shared_constants.h
│   │   ├── SharedService.cpp
│   │   ├── SharedService.h
│   │   ├── SharedService_server.skeleton.cpp
│   │   ├── shared_types.cpp
│   │   ├── shared_types.h
│   │   ├── tutorial_constants.cpp
│   │   ├── tutorial_constants.h
│   │   ├── tutorial_types.cpp
│   │   └── tutorial_types.h
│   ├── idl.pro
│   ├── shared.out
│   ├── shared.thrift
│   ├── tutorial.out
│   └── tutorial.thrift