Fix build from docker build with alpine from macOS (#286)

* fix(build): Remove unused variable and fix const warning.
* fix(build): Fix others -Werror=discarded-qualifiers
Co-authored-by: Élie BRAMI <Et7f3@mbp-de-elie.home>

dsp/core/byte2double.c

@@ -22,7 +22,7 @@
 void *byte2double(long n, const void *p, double weight, double bias) {
   long i;
   double f, *dst;
-  unsigned char *src;
+  const unsigned char *src;
   if ((dst = valloc(n * sizeof(double)))) {
     for (src = p, i = 0; i < n; ++i) {
       f = src[i];

dsp/core/dct.c

@@ -21,7 +21,7 @@
 #define DCT(A, B, C, D, E, F, G, H, T, C0, C1, C2, C3, C4)    \
   do {                                                        \
     T z1, z2, z3, z4, z5, z11, z13;                           \
-    T t0, t1, t2, t3, t4, t5, t6, t7, t8, t10, t11, t12, t13; \
+    T t0, t1, t2, t3, t4, t5, t6, t7, t10, t11, t12, t13;     \
     t0 = A + H;                                               \
     t7 = A - H;                                               \
     t1 = B + G;                                               \

dsp/core/float2short.c

@@ -30,7 +30,6 @@
  */
 void float2short(size_t n, short pcm16[n][8], const float binary32[n][8]) {
   size_t i, j;
-  float f[8], w[8];
   for (i = 0; i < n; ++i) {
     for (j = 0; j < 8; ++j) {
       pcm16[i][j] =

dsp/core/unalaw.c

@@ -27,7 +27,7 @@
  * @see ITU G.711
  */
 int unalaw(int x) {
-  int e, i, m, r;
+  int e, i, m;
   i = (x ^ 85) & 127;
   e = i >> 4;
   m = i & 15;

libc/alg/bisect.internal.h

@@ -21,7 +21,7 @@ forceinline void *bisect(const void *k, const void *data, size_t n, size_t size,
       } else if (c < 0) {
         r = m - 1;
       } else {
-        return p + m * size;
+        return (char *)p + m * size;
       }
     }
   }

libc/alg/critbit0_emplace.c

@@ -67,7 +67,7 @@ different_byte_found:
   struct CritbitNode *newnode = malloc(sizeof(struct CritbitNode));
   newnode->byte = newbyte;
   newnode->otherbits = newotherbits;
-  newnode->child[1 - newdirection] = ubytes;
+  newnode->child[1 - newdirection] = (void*)ubytes;
   void **wherep = &t->root;
   for (;;) {
     unsigned char *wp = *wherep;

libc/alg/critbit0_get.c

@@ -39,5 +39,5 @@ char *critbit0_get(struct critbit0 *t, const char *u) {
     const int direction = (1 + (q->otherbits | c)) >> 8;
     p = q->child[direction];
   }
-  return strncmp(u, (const char *)p, ulen) == 0 ? (const char *)p : NULL;
+  return strncmp(u, (char *)p, ulen) == 0 ? (char *)p : NULL;
 }