sh: Fix up __attribute__((optimize ("Os"))) handling on SH [PR105069]

sh: Fix up __attribute__((optimize ("Os"))) handling on SH [PR105069]

As mentioned in the PR, various tests on sh-elf ICE like:
make check-gcc RUNTESTFLAGS="compile.exp='pr104327.c pr58332.c pr81360.c pr84425.c'"
FAIL: gcc.c-torture/compile/pr104327.c   -O0  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr104327.c   -O0  (test for excess errors)
FAIL: gcc.c-torture/compile/pr104327.c   -O1  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr104327.c   -O1  (test for excess errors)
FAIL: gcc.c-torture/compile/pr104327.c   -O2  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr104327.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/compile/pr104327.c   -O3 -g  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr104327.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/compile/pr104327.c   -Os  (test for excess errors)
FAIL: gcc.c-torture/compile/pr58332.c   -O0  (test for excess errors)
FAIL: gcc.c-torture/compile/pr58332.c   -O1  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr58332.c   -O1  (test for excess errors)
FAIL: gcc.c-torture/compile/pr58332.c   -O2  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr58332.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/compile/pr58332.c   -O3 -g  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr58332.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/compile/pr58332.c   -Os  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr58332.c   -Os  (test for excess errors)
FAIL: gcc.c-torture/compile/pr81360.c   -O0  (test for excess errors)
FAIL: gcc.c-torture/compile/pr81360.c   -O1  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr81360.c   -O1  (test for excess errors)
FAIL: gcc.c-torture/compile/pr81360.c   -O2  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr81360.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/compile/pr81360.c   -O3 -g  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr81360.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/compile/pr81360.c   -Os  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr81360.c   -Os  (test for excess errors)
FAIL: gcc.c-torture/compile/pr84425.c   -O0  (test for excess errors)
FAIL: gcc.c-torture/compile/pr84425.c   -O1  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr84425.c   -O1  (test for excess errors)
FAIL: gcc.c-torture/compile/pr84425.c   -O2  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr84425.c   -O2  (test for excess errors)
FAIL: gcc.c-torture/compile/pr84425.c   -O3 -g  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr84425.c   -O3 -g  (test for excess errors)
FAIL: gcc.c-torture/compile/pr84425.c   -Os  (internal compiler error: 'global_options' are modified in local context)
FAIL: gcc.c-torture/compile/pr84425.c   -Os  (test for excess errors)
With the following patch, none of those tests ICE anymore, though
pr104327.c still FAILs with:
Excess errors:
/usr/src/gcc/gcc/testsuite/gcc.c-torture/compile/pr104327.c:6:1: error: inlining failed in call to 'always_inline' 'bar': target specific option mismatch
I think that would be fixable by overriding TARGET_CAN_INLINE_P
hook and allowing at least for always_inline changes in sh_div_str.

2022-04-06  Jakub Jelinek  <jakub@redhat.com>

	PR target/105069
	* config/sh/sh.opt (mdiv=): Add Save.