headers=True option for ms-gsl

conanfile.py

@@ -40,7 +40,7 @@ def requirements(self):
         self.tool_requires("cmake/[>=3.19]")
         self.requires("fmilibrary/[~2.3]")
         self.requires("libzip/[>=1.7 <1.10]") # 1.10 deprecates some functions we use
-        self.requires("ms-gsl/[>=3 <5]", transitive_headers=True)
+        self.requires("ms-gsl/[>=3 <5]", transitive_headers=True, headers=True)
         if self.options.proxyfmu:
             self.requires("proxyfmu/0.3.2@osp/stable")
             self.requires("boost/[~1.81]", transitive_headers=True, transitive_libs=True) # Required by Thrift