clover/api: Support MSVC

Three things:
1. MSVC dislikes mismatching declaration/definition of __declspec(dllexport).
   Since CL headers don't have the declspec, the implementations should't either.
2. An unnamed brace-initialization gets deduced as an initializer list, instead
   of a brace-constructed string. Just add the type name.
3. posix_memalign doesn't exist on Windows.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7680>

src/gallium/frontends/clover/api/memory.cpp

@@ -511,6 +511,7 @@ clSVMAlloc(cl_context d_ctx,
    if (!alignment)
       alignment = 0x80; // sizeof(long16)
 
+#if HAVE_POSIX_MEMALIGN
    bool can_emulate = all_of(std::mem_fn(&device::has_system_svm), ctx.devices());
    if (can_emulate) {
       // we can ignore all the flags as it's not required to honor them.
@@ -520,6 +521,7 @@ clSVMAlloc(cl_context d_ctx,
       posix_memalign(&ptr, alignment, size);
       return ptr;
    }
+#endif
 
    CLOVER_NOT_SUPPORTED_UNTIL("2.0");
    return nullptr;

src/gallium/frontends/clover/api/program.cpp

@@ -123,7 +123,7 @@ clCreateProgramWithBinary(cl_context d_ctx, cl_uint n,
             return { CL_INVALID_VALUE, {} };
 
          try {
-            std::stringbuf bin( { (char*)p, l } );
+            std::stringbuf bin( std::string{ (char*)p, l } );
             std::istream s(&bin);
 
             return { CL_SUCCESS, module::deserialize(s) };

src/gallium/frontends/clover/api/util.hpp

@@ -29,8 +29,12 @@
 #include "core/error.hpp"
 #include "core/property.hpp"
 #include "util/algorithm.hpp"
+#include "util/detect_os.h"
 
-#ifdef HAVE_CLOVER_ICD
+#if DETECT_OS_WINDOWS
+#define CLOVER_API
+#define CLOVER_ICD_API
+#elif HAVE_CLOVER_ICD
 #define CLOVER_API
 #define CLOVER_ICD_API PUBLIC
 #else