make unit test helpers static

Author: solidpixel

Source/UnitTest/test_simd.cpp

@@ -36,7 +36,7 @@ namespace astcenc
  *
  * The value of @c a is stored to lane 0 (LSB) in the SIMD register.
  */
-vfloat8 vfloat8_lit(
+static vfloat8 vfloat8_lit(
 	float a, float b, float c, float d,
 	float e, float f, float g, float h
 ) {
@@ -52,7 +52,7 @@ vfloat8 vfloat8_lit(
  *
  * The value of @c a is stored to lane 0 (LSB) in the SIMD register.
  */
-vint8 vint8_lit(
+static vint8 vint8_lit(
 	int a, int b, int c, int d,
 	int e, int f, int g, int h
 ) {