Add virtual Provide for xxhash-static in xxhash-devel

By setting XXH_INLINE_ALL, xxhash may be used as a header-only library.
This commit adds the virtual Provide that dependent packages that use
xxhash this way are required to BuildRequire. See
https://docs.fedoraproject.org/en-US/packaging-guidelines/#_packaging_header_only_libraries.

xxhash.spec

@@ -1,6 +1,6 @@
 Name:		xxhash
 Version:	0.8.0
-Release:	2%{?dist}
+Release:	3%{?dist}
 Summary:	Extremely fast hash algorithm
 
 #		The source for the library (xxhash.c and xxhash.h) is BSD
@@ -37,6 +37,9 @@ platforms (little / big endian).
 Summary:	Extremely fast hash algorithm - development files
 License:	BSD
 Requires:	%{name}-libs%{?_isa} = %{version}-%{release}
+# By setting XXH_INLINE_ALL, xxhash may be used as a header-only library.
+# Dependent packages that use xxhash this way must BR this virtual Provide:
+Provides:	%{name}-static = %{version}-%{release}
 
 %description devel
 Development files for the xxhash library
@@ -89,6 +92,9 @@ make test-xxhsum-c
 %{_libdir}/pkgconfig/libxxhash.pc
 
 %changelog
+* Thu Jun 10 2021 Benjamin A. Beasley <code@musicinmybrain.net> - 0.8.0-3
+- Add virtual Provide for xxhash-static in xxhash-devel
+
 * Thu Jan 28 2021 Fedora Release Engineering <releng@fedoraproject.org> - 0.8.0-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_34_Mass_Rebuild