build: bundle-libraries.sh: do not override argv[0] in inner exec calls

build: bundle-libraries.sh: do not override argv[0] in inner exec calls

Only mangle argv[0] of the first executed process and leave the argument
vector of subsequent invocations as-is to allow child programs to properly
discover resources relative to their binary locations.

Fixes "cc1" discovery when executing the host gcc through the bundled
"ccache" executable.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>