Fix compilation on Solaris with Sun/Solaris Studio

* Update our Makefile conditional to check for 'sun' and 'studio'
  individually, as vanilla solaris doesn't have `grep -E`
* Add `__sun` to our `PTHREAD_ONCE` detection.

Signed-off-by: michael-grunder <michael.grunder@gmail.com>

Author: michael-grunder

Makefile

@@ -199,7 +199,15 @@ else ifeq ($(uname_S),FreeBSD)
     PTHREAD_FLAGS += -pthread
   endif
 else ifeq ($(uname_S),SunOS)
-  ifeq ($(shell $(CC) -V 2>&1 grep -iq 'sun\|studio' && echo true),true)
+  # Solaris' default grep doesn't have -E so we need two checks
+  CC_VERSION := $(shell $(CC) -V 2>&1 || echo unknown)
+  ifneq (,$(findstring Sun C,$(CC_VERSION)))
+    HAVE_SUN_CC := 1
+  else ifneq (,$(findstring Studio,$(CC_VERSION)))
+    HAVE_SUN_CC := 1
+  endif
+
+  ifeq ($(HAVE_SUN_CC),1)
     SUN_SHARED_FLAG = -G
     REAL_CFLAGS    += -mt
     ifeq ($(USE_THREADS),1)

src/conn.c

@@ -34,7 +34,7 @@
 
 #ifdef VALKEY_USE_THREADS
 
-#if defined(__unix__) || defined(__APPLE__)
+#if defined(__unix__) || defined(__APPLE__) || defined(__sun)
 #define VALKEY_PTHREADS_ONCE 1
 #elif defined(_WIN32)
 #define VALKEY_WINDOWS_ONCE 1