build: fix MSVC build after subtree update

Co-authored-by: Hennadii Stepanov <[email protected]>
Co-authored-by: Aaron Clauson <[email protected]>

Author: 3 people

build_msvc/libsecp256k1/libsecp256k1.vcxproj

@@ -8,6 +8,8 @@
     <ConfigurationType>StaticLibrary</ConfigurationType>
   </PropertyGroup>
   <ItemGroup>
+    <ClCompile Include="..\..\src\secp256k1\src\precomputed_ecmult.c" />
+    <ClCompile Include="..\..\src\secp256k1\src\precomputed_ecmult_gen.c" />
     <ClCompile Include="..\..\src\secp256k1\src\secp256k1.c" />
   </ItemGroup>
   <ItemDefinitionGroup>