Program::shader() now only takes a void* + size

Program::shader() was taking a string before which didn't make sense
for spirv.  Now it's just a blob, in the case of GL/Metal, the blob
must be a null terminated c-string, and the size must include the
terminating null character.

This fixes an out-of-bound access in ShaderBuilder::getShader() (which
doesn't exist anymore), because it was creating a CString passing
a size that included the null terminating char, which is not was CString
expects. CString can now assert() in that case.


driver::Program now uses a std::vector<> for storage, which we should
fix at some point (b/c it's a public header). CString was not suited to
store binary blobs.

libs/utils/src/CString.cpp

@@ -35,9 +35,7 @@ int StaticString::compare(const StaticString& rhs) const noexcept {
 UTILS_NOINLINE
 CString::CString(const char* cstr, size_type length) {
     if (length && cstr) {
-        // I think we can't use this assert with vulkan, because shaders are returned as CString
-        // (see ShaderBuilder).
-        // assert(length == strlen(cstr));
+        assert(length == strlen(cstr));
         Data* p = (Data*)malloc(sizeof(Data) + length + 1);
         p->length = length;
         mCStr = (value_type*)(p + 1);