Properly support -fPIE by linking PIE binaries with specially-built
Scrt1.o instead of crt1.o, since the later is built as non-PIC.
Separate i386-elf crt1.c into the pure assembler part and C code,
supplying all data extracted by assembler stub as explicit parameters.
Hide and localize _start1 symbol used as an interface between asm and
C code.
5300f787ac