depends: modify FastFixedDtoa optimisation flags

This fixes a non-determinism issue in the asm produced for
this function when cross-compiling on x86_64 and aarch64 for
the arm-linux-gnueabihf HOST.

Related to #21194.

depends/patches/qt/fast_fixed_dtoa_no_optimize.patch

@@ -0,0 +1,20 @@
+Modify the optimisation flags for FastFixedDtoa.
+This fixes a non-determinism issue in the asm produced for
+this function when cross-compiling on x86_64 and aarch64 for
+the arm-linux-gnueabihf HOST.
+
+--- a/qtbase/src/3rdparty/double-conversion/fixed-dtoa.h
++++ b/qtbase/src/3rdparty/double-conversion/fixed-dtoa.h
+@@ -48,9 +48,12 @@ namespace double_conversion {
+ //
+ // This method only works for some parameters. If it can't handle the input it
+ // returns false. The output is null-terminated when the function succeeds.
++#pragma GCC push_options
++#pragma GCC optimize ("-O1")
+ bool FastFixedDtoa(double v, int fractional_count,
+                    Vector<char> buffer, int* length, int* decimal_point);
+ 
++#pragma GCC pop_options
+ }  // namespace double_conversion
+ 
+ #endif  // DOUBLE_CONVERSION_FIXED_DTOA_H_