Allow multi-word "install" command.

Autoconf can determine that the correct install command includes flags,
e.g., "/usr/bin/install -c". When using this as a command, we can't
enclose the value in double-quotes, as that makes some shells use the
whole expression as a filename:

# this is the value returned by autoconf and stored in CT_install
$ ins="/usr/bin/install -c"

# if we call it with quotes, the command is not found
$ "${ins}"
bash: /usr/bin/install -c: No such file or directory

# removing the quotes lets it work as expected
$ ${ins}
/usr/bin/install: missing file operand
Try `/usr/bin/install --help' for more information.

Signed-Off-By: Anthony Foiani <anthony.foiani@gmail.com>

 # MIPS specific config options

 choice

     bool

     prompt "ABI"

 config ARCH_mips_o32

     bool

     prompt "o32"

     depends on ARCH_32

     help

       This is the -mabi=32 gcc option.

 config ARCH_mips_n32

     bool

     prompt "n32"

     depends on ARCH_64

     help

       This is the -mabi=n32 gcc option.

 config ARCH_mips_n64

     bool

     prompt "n64"

     depends on ARCH_64

     help

       This is the -mabi=64 gcc option.

 # Not supported on Linux:

 # o64   : seems related to *BSD

 # eabi  : seems related to bare-metal

 endchoice

 config ARCH_mips_ABI

     string

     default "32"    if ARCH_mips_o32

     default "n32"   if ARCH_mips_n32

     default "64"    if ARCH_mips_n64