Use -Os for NO_UDBL_DIVISION and NO_64BIT_MULTIPLICATION

Build with -Os when testing that the options MBEDTLS_NO_UDBL_DIVISION
and MBEDTLS_NO_64BIT_MULTIPLICATION cause the forbidden auxiliary
function not to be used. -Os is more likely to cause the function not
to be inlined, and it's also the option that's most likely to be used
on these targets.

In the arm build with the default configuration, keep -O0 for variety.
Pass it explicitly for clarity.

tests/scripts/all.sh

@@ -1075,9 +1075,9 @@ component_test_no_64bit_multiplication () {
 }
 
 component_build_arm_none_eabi_gcc () {
-    msg "build: arm-none-eabi-gcc, make" # ~ 10s
+    msg "build: arm-none-eabi-gcc -O0, make" # ~ 10s
     scripts/config.pl baremetal
-    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -Wall -Wextra' lib
+    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -Wall -Wextra -O0' lib
 }
 
 component_build_arm_none_eabi_gcc_armel () {
@@ -1090,7 +1090,7 @@ component_build_arm_none_eabi_gcc_no_udbl_division () {
     msg "build: arm-none-eabi-gcc -DMBEDTLS_NO_UDBL_DIVISION, make" # ~ 10s
     scripts/config.pl baremetal
     scripts/config.pl set MBEDTLS_NO_UDBL_DIVISION
-    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -Wall -Wextra' lib
+    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -Wall -Wextra -Os' lib
     echo "Checking that software 64-bit division is not required"
     if_build_succeeded not grep __aeabi_uldiv library/*.o
 }
@@ -1099,7 +1099,7 @@ component_build_arm_none_eabi_gcc_no_64bit_multiplication () {
     msg "build: arm-none-eabi-gcc MBEDTLS_NO_64BIT_MULTIPLICATION, make" # ~ 10s
     scripts/config.pl baremetal
     scripts/config.pl set MBEDTLS_NO_64BIT_MULTIPLICATION
-    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -O1 -march=armv6-m -mthumb' lib
+    make CC=arm-none-eabi-gcc AR=arm-none-eabi-ar LD=arm-none-eabi-ld CFLAGS='-Werror -Os -march=armv6-m -mthumb' lib
     echo "Checking that software 64-bit multiplication is not required"
     if_build_succeeded not grep __aeabi_lmul library/*.o
 }