[gdb/testsuite] Convert multi-line function call into single line.

[gdb/testsuite] Convert multi-line function call into single line.

    After this clang backend patch(https://reviews.llvm.org/D91734), 8 test points
    started to FAIL in this test case. As mentioned in this PR, "...this test is
    trying to next over a function call; gcc attributes all parameter evaluation
    to the function name, while clang will attribute each parameter to its own
    location. And when the parameters span across multiple source lines, the
    is_stmt heuristic kicks in, so we stop on each line with actual parameters...".

    gdb.base/foll-exec.c test file snippet :
    . . .
     42   execlp (prog, /* tbreak-execlp */
     43           prog,
     44           "execlp arg1 from foll-exec",
     45           (char *) 0);
     46
     47   printf ("foll-exec is about to execl(execd-prog)...\n");
    . . .

    Line table: (before clang backend patch for the above code snippet) :
    0x000000b0: 84 address += 8,  line += 2
                0x000000000020196a     42      3      1   0             0
    0x000000b1: 08 DW_LNS_const_add_pc (0x0000000000000011)
    0x000000b2: 41 address += 3,  line += 5
                0x000000000020197e     47      3      1   0             0

    Line table: (after clang backend patch for the above code snippet) :
    0x000000b5: 84 address += 8,  line += 2
                0x0000000000201958     42     11      1   0             0
    0x000000b6: 05 DW_LNS_set_column (4)
    0x000000b8: 75 address += 7,  line += 1
                0x000000000020195f     43      4      1   0             0
    0x000000b9: 05 DW_LNS_set_column (3)
    0x000000bb: 73 address += 7,  line += -1
                0x0000000000201966     42      3      1   0             0
    0x000000bc: 08 DW_LNS_const_add_pc (0x0000000000000011)
    0x000000bd: 4f address += 4,  line += 5
                0x000000000020197b     47      3      1   0             0

    Following 8 test points started to fail after the above clang backend patch.

    FAIL: gdb.base/foll-exec.exp: step through execlp call
    FAIL: gdb.base/foll-exec.exp: step after execlp call
    FAIL: gdb.base/foll-exec.exp: print execd-program/global_i (after execlp)
    FAIL: gdb.base/foll-exec.exp: print execd-program/local_j (after execlp)
    FAIL: gdb.base/foll-exec.exp: print follow-exec/local_k (after execlp)
    FAIL: gdb.base/foll-exec.exp: step through execl call
    FAIL: gdb.base/foll-exec.exp: step after execl call
    FAIL: gdb.base/foll-exec.exp: print execd-program/local_j (after execl)

    As we can note, reason for these new test failures is due to additional
    .debug_line entries getting created in case of clang compiler, hence to fix
    this issue, test case required either additional next command during
    these multi-line function call or combine these multi-line function call into
    single line. This PR has taken the latter approach and converted the multi-line
    function call into single line in foll-exec.c, thereby there is no change in
    .debug_line entries now and test case works as expected.