[Bug target/87391] [RISCV] -march=rv32i -mabi=ilp32e is erroneously accepted

[asb at lowrisc dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87391

--- Comment #1 from Alex Bradbury <asb at lowrisc dot org> ---
Apologies I pasted the wrong command output in the original report. The
invocation demonstrating the bug is below:

$ ./riscv32-unknown-elf-gcc -march=rv32i -mabi=ilp32e foo.c -S -o -
        .file   "foo.c"
        .option nopic
        .text
        .align  2
        .globl  bar
        .type   bar, @function
bar:
        addi    sp,sp,-16
        sw      ra,12(sp)
        sw      s0,8(sp)
        addi    s0,sp,16
        li      a6,7
        li      a5,6
        li      a4,5
        li      a3,4
        li      a2,3
        li      a1,2
        li      a0,1
        call    foo
        mv      a5,a0
        mv      a0,a5
        lw      ra,12(sp)
        lw      s0,8(sp)
        addi    sp,sp,16
        jr      ra
        .size   bar, .-bar
        .ident  "GCC: (GNU) 9.0.0 20180922 (experimental)"