mgard: don't restrict protobuf version more than necessary (spack#43172)

* mgard: don't restrict protobuf version more than necessary

successfully built:
mgard@2022-11-18 ^protobuf@3.{4,21,25}
mgard@2023-01-10 ^protobuf@3.{4,25}
mgard@2023-03-31 ^protobuf@3.{4,25}

compile failures:
mgard@2022-11-18 ^[email protected]
mgard@2023-01-10 ^[email protected]
mgard@2023-03-31 ^[email protected]

* mgard: add conflicts to address CI errors

* mgard: conflict between cuda and [email protected]

compiling mgard+cuda with [email protected] and nvcc from [email protected] against
protobuf pulling in [email protected] results in the errors reported
here: abseil/abseil-cpp#1629

var/spack/repos/builtin/packages/mgard/package.py

@@ -49,7 +49,7 @@ class Mgard(CMakePackage, CudaPackage):
     depends_on("zlib-api")
     depends_on("pkgconfig", type=("build",), when="@2022-11-18:")
     depends_on("zstd")
-    depends_on("protobuf@:3.21.12", when="@2022-11-18:")
+    depends_on("protobuf@3.4:", when="@2022-11-18:")
     depends_on("libarchive", when="@2021-11-12:")
     depends_on("tclap", when="@2021-11-12")
     depends_on("yaml-cpp", when="@2021-11-12:")
@@ -64,6 +64,10 @@ class Mgard(CMakePackage, CudaPackage):
         "~cuda", when="@2021-11-12", msg="without cuda MGARD@2021-11-12 has undefined symbols"
     )
     conflicts("%gcc@:7", when="@2022-11-18:", msg="requires std::optional and other c++17 things")
+    conflicts("[email protected]:", when="target=ppc64le", msg="GCC 9.4 segfault in CI")
+    conflicts("[email protected]:", when="+cuda target=aarch64:", msg="nvcc fails on ARM SIMD headers")
+    # https://github.com/abseil/abseil-cpp/issues/1629
+    conflicts("[email protected]", when="+cuda", msg="triggers nvcc parser bug")
 
     def flag_handler(self, name, flags):
         if name == "cxxflags":