NSPR does not know that gcc does work on AIX:
https://bugzilla.mozilla.org/show_bug.cgi?id=547991

--- ./mozilla/nsprpub/configure.in.orig	2010-02-23 14:36:55 +0100
+++ ./mozilla/nsprpub/configure.in	2010-02-23 14:37:08 +0100
@@ -871,8 +871,13 @@
         AC_DEFINE(HAVE_FCNTL_FILE_LOCKING)
         USE_IPV6=1
         AIX_LINK_OPTS='-brtl -bnso -berok'
+        if test -n "$GNU_CC"; then
+            LD='$(CC)'
+            DSO_LDOPTS='-shared -Wl,-G,-bernotok,-bexpall,-blibpath:/usr/lib:/lib'
+        fi
         ;;
     esac
+    test -z "$GNU_CC" &&
     CFLAGS="$CFLAGS -qro -qroconst"
     AIX_WRAP='$(DIST)/lib/aixwrap.o'
     AIX_TMP='./_aix_tmp.o'
--- ./mozilla/nsprpub/configure.orig	2010-02-23 14:36:58 +0100
+++ ./mozilla/nsprpub/configure	2010-02-23 14:37:08 +0100
@@ -3099,8 +3099,13 @@
 
         USE_IPV6=1
         AIX_LINK_OPTS='-brtl -bnso -berok'
+        if test -n "$GNU_CC"; then
+            LD='$(CC)'
+            DSO_LDOPTS='-shared -Wl,-G,-bernotok,-bexpall,-blibpath:/usr/lib:/lib'
+        fi
         ;;
     esac
+    test -z "$GNU_CC" &&
     CFLAGS="$CFLAGS -qro -qroconst"
     AIX_WRAP='$(DIST)/lib/aixwrap.o'
     AIX_TMP='./_aix_tmp.o'
--- ./mozilla/nsprpub/lib/ds/Makefile.in.orig	2010-02-23 14:40:10 +0100
+++ ./mozilla/nsprpub/lib/ds/Makefile.in	2010-02-23 14:40:58 +0100
@@ -68,11 +68,19 @@
 endif # WINNT
 
 ifeq ($(OS_ARCH), AIX)
+ifndef NS_USE_GCC
 ifeq ($(CLASSIC_NSPR),1)
 OS_LIBS = -lc
 else
 OS_LIBS = -lc_r
 endif
+else
+ifeq ($(CLASSIC_NSPR),1)
+OS_LIBS =
+else
+OS_LIBS = -pthread
+endif
+endif
 endif
 
 ifeq ($(OS_ARCH),IRIX)
--- ./mozilla/nsprpub/lib/libc/src/Makefile.in.orig	2010-02-23 14:45:41 +0100
+++ ./mozilla/nsprpub/lib/libc/src/Makefile.in	2010-02-23 14:47:58 +0100
@@ -77,11 +77,19 @@
 endif # WINNT
 
 ifeq ($(OS_ARCH), AIX)
+ifndef NS_USE_GCC
 ifeq ($(CLASSIC_NSPR),1)
 OS_LIBS = -lc
 else
 OS_LIBS = -lc_r
 endif
+else
+ifeq ($(CLASSIC_NSPR),1)
+OS_LIBS =
+else
+OS_LIBS = -pthread
+endif
+endif
 endif
 
 ifeq ($(OS_ARCH),IRIX)
--- ./mozilla/nsprpub/pr/src/Makefile.in.orig	2010-02-23 14:37:04 +0100
+++ ./mozilla/nsprpub/pr/src/Makefile.in	2010-02-23 14:52:16 +0100
@@ -110,19 +110,29 @@
 endif
 
 ifeq ($(OS_ARCH),AIX)
+ifndef NS_USE_GCC
 DSO_LDOPTS	+= -binitfini::_PR_Fini
+endif
 OS_LIBS		= -lodm -lcfg
 ifeq ($(CLASSIC_NSPR),1)
 ifeq ($(OS_RELEASE),4.1)
 OS_LIBS		+= -lsvld -lc
 else
+ifndef NS_USE_GCC
 OS_LIBS		+= -ldl -lc
+else
+OS_LIBS		+= -ldl
+endif
 endif
 else
 ifeq ($(OS_RELEASE),4.1)
 OS_LIBS		+= -lpthreads -lsvld -lC_r -lC -lc_r -lm /usr/lib/libc.a
 else
+ifndef NS_USE_GCC
 OS_LIBS		+= -lpthreads -ldl -lC_r -lC -lc_r -lm /usr/lib/libc.a
+else
+OS_LIBS		+= -pthread -ldl -lm
+endif
 endif
 endif
 endif
--- mozilla/nsprpub/pr/tests/Makefile.in.orig	2010-02-23 15:14:03 +0100
+++ mozilla/nsprpub/pr/tests/Makefile.in	2010-02-23 15:17:58 +0100
@@ -341,9 +341,17 @@
 
 # AIX
 ifeq ($(OS_ARCH),AIX)
+  ifndef NS_USE_GCC
     LDOPTS += -blibpath:$(ABSOLUTE_LIB_DIR):/usr/lib:/lib
+  else
+    LDOPTS += -Wl,-blibpath:$(ABSOLUTE_LIB_DIR):/usr/lib:/lib
+  endif
     ifneq ($(OS_ARCH)$(OS_RELEASE),AIX4.1)
+      ifndef NS_USE_GCC
         LDOPTS += -brtl
+      else
+        LDOPTS += -Wl,-brtl
+      endif
         EXTRA_LIBS = -ldl
     endif
 endif
--- mozilla/nsprpub/lib/tests/Makefile.in.orig	2010-02-23 15:35:37 +0100
+++ mozilla/nsprpub/lib/tests/Makefile.in	2010-02-23 15:35:37 +0100
@@ -127,7 +127,11 @@
 
 # AIX
 ifeq ($(OS_ARCH),AIX)
+ifndef NS_USE_GCC
 LDOPTS += -blibpath:$(PWD)/$(dist_libdir):/usr/lib:/lib
+else
+LDOPTS += -Wl,-blibpath:$(PWD)/$(dist_libdir):/usr/lib:/lib
+endif
 LIBPR = -lnspr$(MOD_MAJOR_VERSION)_shr
 LIBPLC = -lplc$(MOD_MAJOR_VERSION)_shr
 endif