+Basic build
+ make config T=x86_64-native-linuxapp-gcc && make
+Build commands
+ config get configuration from target template (T=)
+ all same as build (default rule)
+ build build in a configured directory
+ clean remove files but keep configuration
+ install T= configure, build and install a target in DESTDIR
+ install install optionally staged in DESTDIR
+ examples build examples for given targets (T=)
+ examples_clean clean examples for given targets (T=)
+Build variables
+ EXTRA_CPPFLAGS preprocessor options
+ EXTRA_CFLAGS compiler options
+ EXTRA_LDFLAGS linker options
+ EXTRA_LDLIBS linker library options
+ RTE_KERNELDIR linux headers path
+ RTE_DEVEL_BUILD stricter options (default: y in git tree)
+ CROSS toolchain prefix
+ V verbose
+ D debug dependencies
+ O build directory (default: build/ - install T= default: ./)
+ DESTDIR staging install directory
+ prefix root install directory
+ T target template - used with config or install
+ format: <arch-machine-execenv-toolchain>
+ templates in config/defconfig_*