Makefile: do not hardcode the `install` program path

On systems that do not use the FHS, such as NixOS, the `install` program is not
located in `/usr/bin/` as its location is dynamic.

`dtc` can be easily installed on such systems by using the `install` program
available in the `$PATH` with:

    make PREFIX=… INSTALL=install

However, this becomes more difficult when `dtc` is being compiled as part of a
larger toolchain, as the toolchain build scripts will not spontaneously pass
such an argument on the command line. This happens for example when `dtc` is
build as a part of the RTEMS build system.

By not hardcoding a predefined path for `install`, as is done for other
executables, `dtc` will allow the one in the `$PATH` to be used.

Signed-off-by: Samuel Tardieu <sam@rfc1149.net>
Message-ID: <20240208191405.1597654-1-sam@rfc1149.net>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Makefile

@@ -29,7 +29,7 @@ SWIG = swig
 PKG_CONFIG ?= pkg-config
 PYTHON ?= python3
 
-INSTALL = /usr/bin/install
+INSTALL = install
 INSTALL_PROGRAM = $(INSTALL)
 INSTALL_LIB = $(INSTALL)
 INSTALL_DATA = $(INSTALL) -m 644