gdb, testsuite, fortran: fixup mixed-lang-stack for Intel/LLVM compilers

When value-printing a pointer within GDB by default GDB will look for
defined symbols residing at the address of the pointer.  For the given
test the Intel/LLVM compiler stacks both display a symbol associated
with a printed pointer while the gnu stack does not.  This leads to
failures in the test when running the test with CC_FOR_TARGET='clang'
CXX_FOR_TARGET='clang' F90_FOR_TARGET='flang'"

  (gdb) b 37
  (gdb) r
  (gdb) f 6
  (gdb) info args
  a = 1
  b = 2
  c = 3
  d = 4 + 5i
  f = 0x419ed0 "abcdef"
  g = 0x4041a0 <.BSS4>

or CC_FOR_TARGET='icx' CXX_FOR_TARGET='icpx' F90_FOR_TARGET='ifx'"

  (gdb) b 37
  (gdb) r
  (gdb) f 6
  (gdb) info args
  a = 1
  b = 2
  c = 3
  d = 4 + 5i
  f = 0x52eee0 "abcdef"
  g = 0x4ca210 <mixed_func_1a_$OBJ>

For the compiled binary the Intel/LLVM compilers both decide to move the
local variable g into the .bss section of their executable.  The gnu
stack will keep the variable locally on the stack and not define a
symbol for it.

Since the behavior for Intel/LLVM is actually expected I adapted the
testcase at this point to be a bit more allowing for other outputs.
I added the optional "<SYMBOLNAME>" to the regex testing for g.

The given changes reduce the test fails for Intel/LLVM stack by 4 each.