Fix unused variable build error in nanosvg.cpp

[Copilot]

The "Build Clover Release" CI job was failing because nsvg__dumpFloat declared variables b and sign that are only referenced inside DBG(...). In release builds, DEBUG_SVG == 0 collapses DBG(...) to a no-op, leaving both variables unused — fatal under -Werror=unused-variable.

Change

Wrapped the debug-only variable declarations and DBG call in nsvg__dumpFloat with #if DEBUG_SVG != 0:

// Before
for(int i=0; i<N;i++)
{
    float a = t[i];
    int b = (int)a;
    int sign = (a < 0.f);
    DBG("%c%d.%06d ", ((b == 0) && sign)?'-':' ', b, (int)(fabsf((a-(float)b)*1.0e6f)));
}

// After
for(int i=0; i<N;i++)
{
#if DEBUG_SVG != 0
    float a = t[i];
    int b = (int)a;
    int sign = (a < 0.f);
    DBG("%c%d.%06d ", ((b == 0) && sign)?'-':' ', b, (int)(fabsf((a-(float)b)*1.0e6f)));
#endif
}

This mirrors the existing DBG macro guard pattern already present in the file and keeps the debug path fully intact.