armv7a9-zynq7000: strtod does not handle negative values

[damianloew]

• Tested on armv7a9-zynq7000-zedboard
• Seems to work properly on ia32-generic-qemu architecture

• How to reproduce:

  • Run the following code on mentioned architecture:

    
    #include <stdio.h>
    #include <stdlib.h>

  int main(void) { printf("strtod(-0.008598) = %lf\n", strtod("-0.008598", NULL)); printf("strtod(-0.5) = %lf\n", strtod("-0.5", NULL)); printf("strtod(-1.0) = %lf\n", strtod("-1.0", NULL)); printf("strtod(-2.99) = %lf\n", strtod("-2.99", NULL)); return 0; }

  
  
  - Result:
  ![Screenshot from 2023-02-15 13-27-33](https://user-images.githubusercontent.com/77304431/219028100-284164fd-4192-4b8a-8421-62c6457665b4.png)

[niewim19]

Recently there was change in strtof/d/ld implementation in libphoenix:

• https://github.com/phoenix-rtos/libphoenix/commit/6b37553265786bb55a85da93d46a627b25749ad0, merged in January

This issue does not occur before this commit. Significant change is that long double is now used to hold conversion value and double was used before (just a clue, not verified).

[nalajcie]

@DawidSzpejna it might be worth to add these tests to https://github.com/phoenix-rtos/phoenix-rtos-tests/pull/135 (actually I see that this test shows error on zynq already)