target compiler flags are used with host compiler

$ ~/Qt/5.9.1/Boot2Qt/apalis-imx6/toolchain/sysroots/x86_64-pokysdk-linux/usr/bin/qmake && make

Building gn manually in a temporary directory for bootstrapping...
ninja: Entering directory `/home/sapiippo/development/qt/qt5/qtwebengine/src/3rdparty/chromium/tools/gn/out/Release'
[330/330] LINK gn
Building gn using itself to out/Release...
Done. Made 5210 targets from 1111 files in 776ms
ninja: Entering directory `/home/sapiippo/development/qt/qt5/qtwebengine/src/3rdparty/chromium/tools/gn/out/Release'
[3/639] CXX obj/base/base_static/switches.o
FAILED: obj/base/base_static/switches.o
/usr/bin/g++ -MMD -MF obj/base/base_static/switches.o.d -DV8_DEPRECATION_WARNINGS -DUSE_UDEV -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DNO_TCMALLOC -DDISABLE_NACL -DENABLE_TASK_MANAGER=1 -DENABLE_THEMES=1 -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED -DTOOLKIT_QT -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -Igen -I../../../.. -fno-strict-aliasing --param=ssp-buffer-size=4 -fstack-protector -funwind-tables -fPIC -pipe -pthread -march=armv7-a -mfloat-abi=hard -mtune=generic-armv7-a -mfpu=neon -mthumb -Wall -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -Wno-psabi -Wno-unused-local-typedefs -Wno-maybe-uninitialized -Wno-missing-field-initializers -Wno-unused-parameter -g0 -fvisibility=hidden -O2 -fno-ident -fdata-sections -ffunction-sections -fno-threadsafe-statics -fvisibility-inlines-hidden -std=gnu++11 -fno-delete-null-pointer-checks -Wno-narrowing -fno-rtti -fno-exceptions -c ../../../../base/task_scheduler/switches.cc -o obj/base/base_static/switches.o
g++: error: unrecognized command line option ‘-mfloat-abi=hard’
g++: error: unrecognized command line option ‘-mfpu=neon’
g++: error: unrecognized command line option ‘-mthumb’