testsuite: Fix up target selector syntax errors in modules/builtin-3*.C [PR99601]

testsuite: Fix up target selector syntax errors in modules/builtin-3*.C [PR99601]

Without this patch I'm seeing:
ERROR: tcl error sourcing /home/jakub/src/gcc/gcc/testsuite/g++.dg/modules/modules.exp.
ERROR: unmatched open brace in list
    while executing
"foreach op $tmp {
        switch [lindex $op 0] {
            "dg-options" {
                set std_prefix "-std=gnu++"
                if { [string match "*-std=*" [lindex $op 2]] } {
                    ..."
    (procedure "module-init" line 7)
    invoked from within
"module-init $src"
    invoked from within
"if [runtest_file_p $runtests $src] {
        set tests [lsort [find [file dirname $src]  [regsub {_a.[CHX]$} [file tail $src] {_[a-z].[CHX]}]]]

        set std_lis..."
    ("foreach" body line 3)
    invoked from within
"foreach src [lsort [find $srcdir/$subdir {*_a.[CHX}]] {
    # use the FOO_a.C name as the parallelization key
    if [runtest_file_p $runtests $src] {..."
    (file "/home/jakub/src/gcc/gcc/testsuite/g++.dg/modules/modules.exp" line 304)
    invoked from within
"source /home/jakub/src/gcc/gcc/testsuite/g++.dg/modules/modules.exp"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 source /home/jakub/src/gcc/gcc/testsuite/g++.dg/modules/modules.exp"
    invoked from within
"catch "uplevel #0 source $test_file_name""

2021-03-16  Jakub Jelinek  <jakub@redhat.com>

	PR c++/99601
	* g++.dg/modules/builtin-3_a.C: Fix target selector syntax errors.
	* g++.dg/modules/builtin-3_b.C: Likewise.