Add linux-musl entry for FALLBACK_HOST_RID (#65339)

* Add linux-musl entry for FALLBACK_HOST_RID

* Stay consistent about host vs. target

* Classify linux-musl agnostic of distro

Author: am11

eng/native/configurecompiler.cmake

@@ -493,10 +493,16 @@ if(CLR_CMAKE_TARGET_UNIX)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_ANDROID>)
   elseif(CLR_CMAKE_TARGET_LINUX)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_LINUX>)
+    if(CLR_CMAKE_TARGET_LINUX_MUSL)
+        add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_LINUX_MUSL>)
+    endif()
   elseif(CLR_CMAKE_TARGET_NETBSD)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_NETBSD>)
   elseif(CLR_CMAKE_TARGET_SUNOS)
     add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_SUNOS>)
+    if(CLR_CMAKE_TARGET_OS_ILLUMOS)
+      add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_ILLUMOS>)
+    endif()
   endif()
 else(CLR_CMAKE_TARGET_UNIX)
   add_compile_definitions($<$<NOT:$<BOOL:$<TARGET_PROPERTY:IGNORE_DEFAULT_TARGET_OS>>>:TARGET_WINDOWS>)

eng/native/configureplatform.cmake

@@ -70,6 +70,11 @@ if(CLR_CMAKE_HOST_OS STREQUAL Linux)
             COMMAND bash -c "source ${LINUX_ID_FILE} && echo \$ID"
             OUTPUT_VARIABLE CLR_CMAKE_LINUX_ID
             OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+        execute_process(
+            COMMAND bash -c "if strings \"${CMAKE_SYSROOT}/usr/bin/ldd\" 2>&1 | grep -q musl; then echo musl; fi"
+            OUTPUT_VARIABLE CLR_CMAKE_LINUX_MUSL
+            OUTPUT_STRIP_TRAILING_WHITESPACE)
     endif()
 
     if(DEFINED CLR_CMAKE_LINUX_ID)
@@ -80,6 +85,10 @@ if(CLR_CMAKE_HOST_OS STREQUAL Linux)
             set(CLR_CMAKE_HOST_ALPINE_LINUX 1)
             set(CLR_CMAKE_HOST_OS ${CLR_CMAKE_LINUX_ID})
         endif()
+
+        if(CLR_CMAKE_LINUX_MUSL STREQUAL musl)
+            set(CLR_CMAKE_HOST_LINUX_MUSL 1)
+        endif()
     endif(DEFINED CLR_CMAKE_LINUX_ID)
 endif(CLR_CMAKE_HOST_OS STREQUAL Linux)
 
@@ -314,6 +323,10 @@ if(CLR_CMAKE_TARGET_OS STREQUAL Linux)
     set(CLR_CMAKE_TARGET_LINUX 1)
 endif(CLR_CMAKE_TARGET_OS STREQUAL Linux)
 
+if(CLR_CMAKE_HOST_LINUX_MUSL)
+    set(CLR_CMAKE_TARGET_LINUX_MUSL 1)
+endif(CLR_CMAKE_HOST_LINUX_MUSL)
+
 if(CLR_CMAKE_TARGET_OS STREQUAL tizen)
     set(CLR_CMAKE_TARGET_UNIX 1)
     set(CLR_CMAKE_TARGET_LINUX 1)

src/native/corehost/hostmisc/hostmisc.cmake

@@ -5,10 +5,6 @@ include(${CMAKE_CURRENT_LIST_DIR}/configure.cmake)
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 include_directories("${CLR_SRC_NATIVE_DIR}")
 
-if(CLR_CMAKE_TARGET_OS_ILLUMOS)
-    add_definitions(-DTARGET_ILLUMOS)
-endif()
-
 # CMake does not recommend using globbing since it messes with the freshness checks
 list(APPEND SOURCES
     ${CMAKE_CURRENT_LIST_DIR}/trace.cpp

src/native/corehost/hostmisc/pal.h

@@ -64,7 +64,7 @@
 // degree of compat across their respective releases is usually high.
 //
 // We cannot maintain the same (compat) invariant for linux and thus, we will fallback to using lowest RID-Plaform.
-#if defined(_WIN32)
+#if defined(TARGET_WINDOWS)
 #define LIB_PREFIX
 #define MAKE_LIBNAME(NAME) (_X(NAME) _X(".dll"))
 #define FALLBACK_HOST_RID _X("win10")
@@ -79,8 +79,10 @@
 #define FALLBACK_HOST_RID _X("freebsd")
 #elif defined(TARGET_ILLUMOS)
 #define FALLBACK_HOST_RID _X("illumos")
-#elif defined(__sun)
+#elif defined(TARGET_SUNOS)
 #define FALLBACK_HOST_RID _X("solaris")
+#elif defined(TARGET_LINUX_MUSL)
+#define FALLBACK_HOST_RID _X("linux-musl")
 #else
 #define FALLBACK_HOST_RID _X("linux")
 #endif