Support building shared libraries or modules without soname (#13155)

Add a boolean target property NO_SONAME which may be used to disable
soname for the specified shared library or module even if the platform
supports it.  This property should be useful for private shared
libraries or various plugins which live in private directories and have
not been designed to be found or loaded globally.

Replace references to <CMAKE_SHARED_LIBRARY_SONAME_${LANG}_FLAG> and
hard-coded -install_name flags with a conditional <SONAME_FLAG> which is
expanded to the value of the CMAKE_SHARED_LIBRARY_SONAME_${LANG}_FLAG
definition as long as soname supports is enabled for the target in
question.  Keep expanding CMAKE_SHARED_LIBRARY_SONAME_${LANG}_FLAG in
rules in case third party projects still use it.  Such projects would
not yet use NO_SONAME so the adjacent <TARGET_SONAME> will always be
expanded.  Make <TARGET_INSTALLNAME_DIR> NO_SONAME aware as well.  Since
-install_name is soname on OS X, this should not be a problem if this
variable is expanded only if soname is enabled.

The Ninja generator performs rule variable substitution only once
globally per rule to put its own placeholders.  Final substitution is
performed by ninja at build time.  Therefore we cannot conditionally
replace the soname placeholders on a per-target basis.  Rather than
omitting $SONAME from rules.ninja, simply do not write its contents for
targets which have NO_SONAME.  Since 3 variables are affected by
NO_SONAME ($SONAME, $SONAME_FLAG, $INSTALLNAME_DIR), set them only if
soname is enabled.

1 files changed, 3 insertions, 0 deletions

diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index 960ba39..ebd5bcf 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -593,6 +593,9 @@ public:
   /** Return whether the target platform is 64-bit.  */
   bool PlatformIs64Bit() const;
 
+  /** Retrieve soname flag for the specified language if supported */
+  const char* GetSONameFlag(const char* language) const;
+
   /**
    * Get a list of preprocessor define flags.
    */