tools build feature: Quote CC and CXX for their arguments

tools build feature: Quote CC and CXX for their arguments

When using a cross-compilation environment, such as OpenEmbedded,
the CC an CXX variables are set to something more than just a
command: there are arguments (such as --sysroot) that need to be
passed on to the compiler so that the right set of headers and
libraries are used.

For the particular case that our systems detected, CC is set to
the following:

  export CC="aarch64-linaro-linux-gcc  --sysroot=/oe/build/tmp/work/machine/perf/1.0-r9/recipe-sysroot"

Without quotes, detection is as follows:

  Auto-detecting system features:
  ...                         dwarf: [ OFF ]
  ...            dwarf_getlocations: [ OFF ]
  ...                         glibc: [ OFF ]
  ...                          gtk2: [ OFF ]
  ...                        libbfd: [ OFF ]
  ...                        libcap: [ OFF ]
  ...                        libelf: [ OFF ]
  ...                       libnuma: [ OFF ]
  ...        numa_num_possible_cpus: [ OFF ]
  ...                       libperl: [ OFF ]
  ...                     libpython: [ OFF ]
  ...                     libcrypto: [ OFF ]
  ...                     libunwind: [ OFF ]
  ...            libdw-dwarf-unwind: [ OFF ]
  ...                          zlib: [ OFF ]
  ...                          lzma: [ OFF ]
  ...                     get_cpuid: [ OFF ]
  ...                           bpf: [ OFF ]
  ...                        libaio: [ OFF ]
  ...                       libzstd: [ OFF ]
  ...        disassembler-four-args: [ OFF ]

  Makefile.config:414: *** No gnu/libc-version.h found, please install glibc-dev[el].  Stop.
  Makefile.perf:230: recipe for target 'sub-make' failed
  make[1]: *** [sub-make] Error 2
  Makefile:69: recipe for target 'all' failed
  make: *** [all] Error 2

With CC and CXX quoted, some of those features are now detected.

Fixes: e3232c2f39ac ("tools build feature: Use CC and CXX from parent")
Signed-off-by: Daniel Díaz <daniel.diaz@linaro.org>
Reviewed-by: Thomas Hebb <tommyhebb@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andriin@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@chromium.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Link: http://lore.kernel.org/lkml/20200812221518.2869003-1-daniel.diaz@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>