Fix problem that would prevent the boot file from being updated.
Fix problem that would prevent the boot file from being updated.

Previously the boot file was read lazily, resulting in it still being open
when the time came to overwrite it with the new boot info. As of this commit,
the boot file is read strictly, and is explicitly closed immediately
afterwards.

kranich/haste-compiler,akru/haste-compiler,jtojnar/haste-compiler,kranich/haste-compiler,joelburget/haste-compiler,szatkus/haste-compiler,nyson/haste-compiler,crodjer/haste-compiler,joelburget/haste-compiler,santolucito/haste-compiler,akru/haste-compiler,kranich/haste-compiler,nyson/haste-compiler,szatkus/haste-compiler,beni55/haste-compiler,crodjer/haste-compiler,joelburget/haste-compiler,santolucito/haste-compiler,jtojnar/haste-compiler,crodjer/haste-compiler,santolucito/haste-compiler,crodjer/haste-compiler,beni55/haste-compiler,nyson/haste-compiler,jtojnar/haste-compiler,beni55/haste-compiler,nyson/haste-compiler,akru/haste-compiler,santolucito/haste-compiler,crodjer/haste-compiler,beni55/haste-compiler,szatkus/haste-compiler,akru/haste-compiler,szatkus/haste-compiler,joelburget/haste-compiler,jtojnar/haste-compiler,akru/haste-compiler,kranich/haste-compiler