NativeBigInteger: Add some indentation to build.sh.
NativeBigInteger: Don't redownload the GMP archive if we already have it.
NativeBigInteger: ARM needs -fPIC as well.

Use a case statement so we can match on regular expressions.
NativeBigInteger: Compile an ARM target on ARM machines.

Use a case statement so we can match on regular expressions and to make adding other archs easier.
NativeBigInteger: Add linux-arm library.

Untested.
NativeBigInteger: Modify the GMP build system to recognise up to ARMv7.

For some reason the regular expression only went up to ARMv5.