runtime/cgo: declare variable setg_gcc as static

variable setg_gcc in runtime/cgo/*.c should be static, otherwise it
will be mixed with the function of the same name in runtime/asm_*.s or
tls_*.s, which causes an error when building PIE with internal linking
mode.

Fixes #31485

Change-Id: I79b311ffcaf450984328db65397840ae7d85e65d
Reviewed-on: https://go-review.googlesource.com/c/go/+/172498Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/cgo/gcc_darwin_arm.c

@@ -47,7 +47,7 @@ inittls(void **tlsg, void **tlsbase)
 }
 
 static void *threadentry(void*);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)

src/runtime/cgo/gcc_darwin_arm64.c

@@ -48,7 +48,7 @@ inittls(void **tlsg, void **tlsbase)
 }
 
 static void *threadentry(void*);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)

src/runtime/cgo/gcc_linux_arm.c

@@ -11,7 +11,7 @@
 static void *threadentry(void*);
 
 void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)

src/runtime/cgo/gcc_linux_arm64.c

@@ -13,7 +13,7 @@
 static void *threadentry(void*);
 
 void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)

src/runtime/cgo/gcc_linux_mips64x.c

@@ -15,7 +15,7 @@
 static void *threadentry(void*);
 
 void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)

src/runtime/cgo/gcc_linux_mipsx.c

@@ -15,7 +15,7 @@
 static void *threadentry(void*);
 
 void (*x_cgo_inittls)(void **tlsg, void **tlsbase);
-void (*setg_gcc)(void*);
+static void (*setg_gcc)(void*);
 
 void
 _cgo_sys_thread_start(ThreadStart *ts)