Honor rpm vendor setting from cmake, use a saner name

The vendor was hardwired to "redhat" as a leftoever from early cmake
bootstrapping phase and bugs in the surrounding logic. Simplify the
setup somewhat: call the setting RPM_VENDOR and pass that around in the
code tree as well. The CANON fubar along with other similar weirdness
can thus remain hidden in the makemacros() cmake function.

Reported and initial patch by Neil Gompa.

CMakeLists.txt

@@ -32,7 +32,7 @@ option(WITH_FSVERITY "Build with fsverity support" OFF)
 option(WITH_IMAEVM "Build with IMA support" OFF)
 
 set(RPMCONFIGDIR "${CMAKE_INSTALL_PREFIX}/lib/rpm" CACHE PATH "rpm home")
-set(RPMCANONVENDOR "vendor" CACHE STRING "rpm vendor string")
+set(RPM_VENDOR "vendor" CACHE STRING "rpm vendor string")
 
 # emulate libtool versioning
 set(RPM_SOVERSION 9)
@@ -90,7 +90,7 @@ function(makemacros)
 
 	set(host_cpu ${CMAKE_HOST_SYSTEM_PROCESSOR})
 	string(TOLOWER ${CMAKE_HOST_SYSTEM_NAME} host_os)
-	set(host_vendor redhat)
+	set(host_vendor ${RPM_VENDOR})
 	set(host ${host_cpu}-${host_vendor}-${host_os})
 
 	set(RPMCANONVENDOR ${host_vendor})

config.h.in

@@ -118,4 +118,4 @@
 #define PACKAGE "@PROJECT_NAME@"
 #define VERSION "@PROJECT_VERSION@"
 #define PACKAGE_BUGREPORT "@PROJECT_HOMEPAGE_URL@"
-#define RPMCANONVENDOR "@RPMCANONVENDOR@"
+#define RPM_VENDOR "@RPM_VENDOR@"

lib/rpmrc.c

@@ -457,7 +457,7 @@ static void setDefaults(void)
     const char *confdir = rpmConfigDir();
     if (!defrcfiles) {
 	defrcfiles = rstrscat(NULL, confdir, "/rpmrc", ":",
-				confdir, "/" RPMCANONVENDOR "/rpmrc", ":",
+				confdir, "/" RPM_VENDOR "/rpmrc", ":",
 				SYSCONFDIR "/rpmrc", ":",
 			  	"~/.rpmrc", NULL);
     }
@@ -468,7 +468,7 @@ static void setDefaults(void)
 				confdir, "/macros.d/macros.*", ":",
 				confdir, "/platform/%{_target}/macros", ":",
 				confdir, "/fileattrs/*.attr", ":",
-  				confdir, "/" RPMCANONVENDOR "/macros", ":",
+  				confdir, "/" RPM_VENDOR "/macros", ":",
 				SYSCONFDIR "/rpm/macros.*", ":",
 				SYSCONFDIR "/rpm/macros", ":",
 				SYSCONFDIR "/rpm/%{_target}/macros", ":",